FIG. V. TAB. III.

_Semiplanum Sphæræ Phonicæ seu Acousticæ._

You are to conceive that (rude) _Semiplane_, as parallel to the

_Horizon_: For if it be perpendicular thereunto, I suppose the upper

extremity will be no longer _Circular_, but _Hyperbolical_, and the

lower part of it suited to a greater Circle of the Earth. So that the

whole _Phonical_ Sphere (if I may so call it) will be a solid

_Hyperbola_, standing upon a _Concave Spherical_ Base. I speak this

concerning _Sounds_ made (as usually they are) nigh the Earth, and whose

Sonorous _Medium_ has a free passage every way. For if they are

generated high in the Air, or directed one way, the case will be

different; which is partly design'd in the inequality of that Draught.

_A Discourse concerning the Modern _Theory_ of _Generation_, by Dr.

_George Garden_ of _Aberdeen_, being part of a Letter to Dr. _William

Musgrave_, L. L. D. Reg. Soc. S. and by him communicated the Royal

Society._

The Subject I pitch upon, is that of the Formation of Animals, You know

how wide and unsatisfying Men's Conjectures were upon this Head, until

this Age, in which first the deservedly Famous Dr. _Harvey_ discovered

the proper place of the Formation of the Chick in the _Cicatricula_ of

the Egg, and the Formation of the Parts so far as was discernable by the

naked Eye; and after him _Malpighius_, by the help of exact Glasses,

observ'd the first Rudiments of it there, both before and after

Incubation: And _R. de Graef_, and others, having upon many Observations

concluded, that the _Testes Fœminei_ were the Ovaries of Females, and

consequently that all Animals were _ex ovo_; they began from hence to

infer, that the Rudiments of each Animal were originally in the

respective Females, and that the Male contributed only to give a new

Ferment to the Mass of the Blood and Spirits, by which means a

spirituous Liquor (which the Blood in its ordinary Ferment could not

produce) did insinuate it self into the same Ducts and Pores of the

Rudiments of those Animals, which were in greatest forwardness in the

Ovary, and so extend and enlarge all their Parts, and at last bring them

to perfection, as Mr. _Perrault_ does ingeniously discourse in the third

Part of his _Essais de Physique_; till now at last _Leowenhoek_ has

discover'd an infinite number of _Animalcula in semine marium_ of all

kinds, which has made him condemn the former Opinions about the

Propagation of all Animals _ex Ovo_.

Now upon comparing the Observations and Discoveries which have been made

with one another, these three things seem to me very probable. 1. That

Animals are _ex Animalculo_. 2. That these Animalcles are originally _in

semine Marium_ & _non in Fœminis_. 3. That they can never come

forward, nor be formed into Animals of the respective kind, without the

_Ova in Fœminis_.

The first of these seems probable from these three Observations. 1. That

some such thing has been so often observ'd by _Malpighius_, in the

_Cicatricula_ of an Egg before Incubation, as the Rudiments of an Animal

in the shape of a Tadpole, as may be seen in his first, and in his

repeated Observations _de formatione Pulli in Ovo_. 2. The sudden

appearance and displaying of all the Parts after Incubation, makes it

probable, that they are not then actually formed out of a fluid, but

that the _Stamina_ of them have been formerly there existent, and are

now expanded. The first Part of the Chick which is discovered with the

naked Eye, is, you know, the _Punctum saliens_, and that not till three

days and nights of Incubation be past; and then, on the fifth day, the

Rudiments of the Head and Body do appear. This made Dr. _Harvey_

conclude, that the Blood had a being before any other Part of the Body;

and that from it, all the Organs of the _Fœtus_ were both form'd and

nourished: But by _Malpighius_'s Observations we find that the Parts are

then only so far extended, as to be made visible to the naked Eye, and

that they were actually existent before, and discernable by Glasses.

After an Incubation of thirty hours, are to be seen the Head, the Eyes,

and the _Carina_ with the _Vertebræ_, distinct, and the Heart. After

forty hours its Pulse is visible, and all the other Parts more distinct,

which cannot be discerned by the naked Eye before the beginning of the

fifth day; from whence it seems probable, that even the so early

discovery of those Parts of the _Fœtus_ by the Microscope, is not the

discerning of Parts newly formed, but only more dilated and extended by

receiving of Nutriment from the _Colliquamentum_; so that they seem all

to have been actually existent before the Incubation of the Hen. And

what _Swammerdam_ has discovered in the transformation of Insects, gives

no small light to this; whilst he makes appear in the Explanation of the

13th Table of the General History of Insects, that in those large

_Eruca's_ which feed upon Cabbage, if they be taken about the time they

retire to be transformed into _Aurelia's_, and plung'd often in warm

Water to make a Rupture of the outer Skin, you will discern through the

transparency of their second Membrane, all the Parts of the Butterfly,

the Trunk, Wings, Feelers, _&c._ folded up. But that after the _Eruca_

is chang'd into an _Aurelia_, none of these Parts can be discern'd, they

are so drencht with moisture, tho' they be there actually form'd.

Another Consideration is from the Analogy, which we may suppose between

Plants and Animals. All Vegetables we do see proceed _ex Plantula_, the

Seeds of Vegetables being nothing else but little Plants of the same

kind folded up in Coats and Membranes; and from hence we may probably

conjecture, that so curiously an organized Creature as an Animal, is not

the sudden Product of a Fluid or _Colliquamentum_, but does much rather

proceed from an Animalcle of the same kind, and has all its little

Members folded up according to their several Joints and Plicatures,

which are afterwards enlarged and distended, as we see in Plants. Now

tho' this Consideration alone may seem not to bear much weight; yet

being join'd to the two former, they do mutually strengthen each other.

And indeed all the Laws of Motion, which are as yet discovered, can give

but a very lame account of the forming of a Plant or Animal. We see how

wretchedly _Des Cartes_ came off when he began to apply them to this

Subject; they are formed by Laws yet unknown to Mankind; and it seems

most probable, that the _Stamina_ of all the Plants and Animals that

have been, or ever shall be in the World, have been form'd, _ab Origine

Mundi_, by the Almighty Creator within the first of each respective

kind. And he who considers the Nature of Vision, that it does not give

us the true magnitude, but the proportion of things; and that what seems

to our naked Eye but a Point, may truly be made up of as many Parts as

seem to us to be in the whole visible World, will not think this an

absurd or impossible thing.

But the second thing which later Discoveries have made probable, is,

that these Animalcles are originally _in Semine Marium_ & _non in

Fœminis_. And this I collect from these Considerations: 1. That there

are innumerable _Animalcula_ discover'd _in Semine Masculo omnium

Animalium_. Mr. _Leewenhoeck_ has made this so evident by so many

Observations, that I do not in the least question the truth of the

thing. The reason of their Multitude, and some of the Difficulties which

arise thereupon, he has cleared to very good Purpose, so that I shall

not repeat them. 2. The observing the Rudiments of the _Fœtus_ in

Eggs, which have been fecundated by the Male, and the seeing no such

thing in those which are not fecundated, as appears from _Malpighius_

his Observations, make it very probable that these Rudiments proceed

originally from the Male, and not from the Female. 3. The resemblance

between the Rudiments of the _Fœtus in Ovo_, both before and after

Incubation, and the _Animalcle_, makes it very probable, that they are

one and the same. The same Shape and Figure which Mr. _Leewenhoeck_

gives us of the _Animalcle_, _Malpighius_ likewise gives of the

Rudiments of the _Fœtus_, both before and after Incubation; yea, and

even the _Fœtus's_ of Animals do appear so at first to the naked Eye,

so that Dr. _Harvey_ does acknowledge that all Animals, even the most

perfect, are begotten of a Worm, _De Gen. Anim. Ex._ 18. 4. This gives a

rational account of many _Fœtus's_ at one Birth, especially that of

the Countess of _Holland_, and how at least a whole Cluster of Eggs in a

Hen are fecundated by one Coition of the Male. 5. This gives a new

light, as it were, to the first Prophecy concerning the _Messiah_, that

the Seed of the Woman shall bruise the Head of the Serpent, all the rest

of Mankind being thus most properly and truly the Seed of the Man.

6. The Analogy I have already mentioned, which we may rationally suppose

between the manner of the propagation of Plants and Animals, does

likewise make this probable. Every Herb and Tree bears its Seed after

its kind; which Seed is nothing else but a little Plant of the same

kind, which being thrown into the Earth, as into its _Uterus_, spreads

forth its Roots, and receives its Nourishment, but has its form within

its self, and we may rationally conjecture some such Analogy in the

Propagation of Animals.

The third Particular which later Discoveries make probable, is, that

Animals cannot be formed of these _Animalcula_ without the _Ova in

fœminis_, which are necessary for supplying of them with proper

Nutriment: And this these Considerations seem to evince. 1. It is

probable that an _Animalcle_ cannot come forward, if it do not fall into

a proper _Nidus_. This we see is the _Cicatricula_ in Eggs; and tho' a

Million of them should fall into an Egg, none of them would come

forward, but what were in the Center of the _Cicatricula_; and perhaps

the _Nidus_ necessary for their formation is so proportion'd to their

bulk, that it can hardly contain more than one _Animalcle_; and this may

be the reason why there are so few Monsters. This we see is absolutely

necessary in _Oviparis_; and the only difference which seems to be

between them and the _Vivipara_, in this matter, is in this, that in the

latter the _Ova_ are properly nothing more but the _Cicatricula_, with

its _Colliquamentum_, so that the _Fœtus_ must spread forth its Roots

into the _Uterus_ to receive its nourishment; but the Eggs in _Oviparis_

may be properly term'd an _Uterus_, in relation to the _Fœtus_; for

they contain not only the _Cicatricula_, with its _Amnion_ and the

_Colliquamentum_, which is the immediate nourishment of the _Fœtus_,

but also the materials which are to be converted into that

_Colliquamentum_; so that the _Fœtus_ spreads forth its Roots no

farther than into the White and Yolk of the Egg, from whence it derives

all its nourishment. Now that an Animalcle cannot come forward without

some such proper _Nidus_, Mr. _Leewenhoeck_ will not readily deny; for

if there were nothing needful, but their being thrown into the _Uterus_,

I do not see why many hundreds of them should not come forward at once;

for as to what Mr. _Leewenhoeck_ says, that one of them would be-dwarf

and choak the rest; this might fall out in process of time: But at first

I do not see why many of them should not grow together, whilst scatter'd

in so large a Field (and yet no such thing is observed) if there were

not an absolute necessity of a _Cicatricula_ for their growth and

thriving. Now, 2. That this _Cicatricula_ is not originally in _Utero_,

seems evident from the frequent Conceptions which have been found _extra

Uterum_: Such as the Child which continued Twenty six Years in the Woman

of _Tholouse_'s Belly, mention'd _Numb._ 139. of the _Philos. Trans._

And the little _Fœtus_ found in the _Abdomen de St. Mere_, together

with the Testicle torn and full of clotted Blood, recorded _Numb._ 150.

both taken out of the Journals _des Savans_: Such also seem to be the

_Fœtus_ in the _Abdomen_ of the Woman of _Copenhagen_, mention'd in

the _Nouvelles des Lettres_, for _Sept._ 85. _pag._ 996. all the Members

of which were easily to be felt through the Skin of the Belly, and which

she had carried in her Belly for four Years; and the seven Years

Gravidation, related by Dr. _Cole_, _Numb._ 172. of the _Transact._ That

these two were undoubtedly _extra Uterum_, is uncertain, because the

last was not open'd after her death, and the former may be yet still

alive. Now granting once the necessity of a proper _Nidus_, for the

formation of an Animalcle into the Animal of its respective kind; these

Observations make it probable, that the _Testes_ are the _Ovaria_

appropriated for this use; for tho' the Animalcles coming thither in

such Cases may seem to be extraordinary, and that usually the

Impregnation is in _Utero_; yet it may be collected from hence, that the

_Cicatriculæ_ or _Ova_ to be impregnated, are in _Testibus fœmineis_;

for if it were not so, the accidental coming of Animalcles thither could

not make them come forward more than in any other part of the Body,

since they cannot be formed and nourished without a proper _Nidus_. But

3. It is acknowledg'd by all, that the _Fœtus in Utero_, for some

considerable time after Conception, has no connexion with the Womb, that

it sits wholly loose to it, and is perfectly a little round Egg with the

_Fœtus_ in the midst, which sends forth its Umbilical Vessels by

degrees, and at last lays hold on the _Uterus_. Now from hence it seems

evident, that the _Cicatricula_, which is the Fountain of the Animalcles

nourishment, does not sprout from the _Uterus_, but has its _Origin_

elsewhere, and falls in thither as into a fit Soil, from whence it may

draw Nutriment for the growth of the _Fœtus_, else it cannot be

easily imagin'd, how it should not have an immediate Connexion with the

_Uterus_ from the time of Conception. If you join all these three

Considerations together, _viz._ that an _Animalcle_ cannot come forward

without a proper _Nidus_ or _Cicatricula_; that there have been frequent

_Fœtus's extra Uterum_; and that they have no _Adhæsion_ to the

_Uterus_, for a considerable time after Conception, they seem to make it

evident, that Animals cannot be form'd _ex Animalculis_ without the _Ova

in Fœminis_. To all these I shall subjoin the Proposal of an

_Experimentum Crucis_, which may seem to determine, whether the _Testes

Fœmineæ_ be truly the _Ovaria_, _viz._ Open the _Abdomen_ of the

Females of some kinds, and cut out these Testicles, and this will

determine, whether they be absolutely necessary for the formation of

Animals.

There are some Difficulties proposed against this Conjecture, which I

think may be easily resolved. Some object the distance between the

_Tubæ_ or _Cornua Uteri_, and the Testicles; but to this is opposed by

_Swammerdam_, and others, the like distance between the _Infundibulum_,

in Hens and Frogs, and the Ovary; and yet it cannot be denied that the

Eggs are transmitted thro' this into the _Uterus_: And besides _R. de

Graef_, and others, have by repeated Observations found that the _Cornua

Uteri_ do at certain times after Conception, embrace the _Testes_ on

both sides the _Uterus_. They object in the second place the great

disproportion between the pretended Eggs in the _Ovary_, and the

Aperture of the _Tubæ_ or _Cornua Uteri_, the former being a great deal

bigger than the latter: But both _R. de Graef_ and _Malpighius_ have

clear'd that Matter, by making appear, that these Bladders in the Ovary

are not the _Ova_, but serve to form the _Glandules_ within which the

_Ova_ are formed, which break through a small _Papilla_ opening in the

_Glandule_, which bears a proportion to the Aperture of the Tube. They

object 3, The difficulty to conceive how these Eggs should be

impregnated _per semen Maris_, both because there is no Connexion

between the _Tubæ_ and the _Ovary_ for its transmission, and for that

Dr. _Harvey_ could never discover any thing of it _in Utero_. As to the

last, Mr. _Leewenhoeck_ has cleared that difficulty, by the discovery of

innumerable _Animalcula Seminis Maris in Cornubus Uteri_, and those

living a considerable time after Coition. _Numb._ 174. of the

_Transact._ And as to the former, we may either suppose that there is

such an Inflation of the _Tubæ_ or _Cornua Uteri tempore Coitionis_, as

makes them embrace the _Ovaria_, and such an approach of the _Uterus_

and its _Cornua_, as that I may easily transmit the Seed into the

_Ovary_; or else, that the _Ova_ are impregnated by the Animalcles after

they descend into the _Uterus_, and not in the _Ovary_; the former seems

probable for this Reason, that at least a whole Cluster of Eggs in a Hen

will be fecundated by one Tread of the Cock: Now this Fecundation seems

to be in the Vitellary, and not in the _Uterus_, as the Eggs pass along

from day to day; for it can hardly be supposed that the Animalcles

should subsist so long, being scattered loosely in the _Uterus_, as to

wait there for many days for the Fecundation of the Eggs as they pass

along. The latter Conjecture has this to strengthen it, that the

Animalcles are found to live a considerable time in the _Uterus_; and

that if they should impregnate the _Ova_ in the Ovary it self, the

_Fœtus_ would increase so fast, that the _Ova_ could not pass through

the _Tubæ Uteri_, but would either burst the Ovary, or fall down into

the Abdomen from the Orifices of the _Tubæ_; and that from hence proceed

those extraordinary Conceptions in _Abdomine extra Uterum_. But, 4. Mr.

_Leewehoeck_, _Numb._ 147. of the _Transact._ to weaken the third

Consideration about the Conceptions, being like unto an _Ovum_ in the

Womb, proposes a Parallel between these Animalcles and Insects; and

insinuates, that as the latter cast their Skins, and appear of another

Shape, so the other which at first seem like Tadpoles, may cast their

outer Skin, and then be round; and that this may be the occasion of the

round Figure of the Conception in the Womb. To this it may be replied,

that according to Mr. _Leewenhoeck_'s own Sentiment, the Animalcles

cannot come forward, if they do not find the _Punctum_ or proper place

for their Nourishment, to which it seems they must have some _Adhæsion_.

Now the Conception in _Viviparis_ is not fastned unto the Womb for many

days, nor does adhere to any point of it; so that it seems this roundish

Body is not the Animalcle thus chang'd after having cast an outer Skin,

but is rather the _Cicatricula_ or little Egg, into which the Animalcle

has entred as its _Punctum_ or place of nourishment; else I do not see

why they should not be adhering to the Womb from the first Conception,

or why (as I have said) many hundreds of them are not conceiv'd and

formed together, _&c._

_A short Discourse concerning Concoction: Read at a Meeting of the Royal

Society, _May ... 1699_, by _Clopton Havers_, M. D. Fellow of the

Royal Society._

The manner in which the Digestion of the Aliment is performed, is a

thing not very easie to be understood and explained. However, it has not

escap'd the Conjectures of some Philosophical Men, who having curiously

observ'd the _Phænomena_ of Nature, and enquired into their Causes,

have, amongst other things, endeavour'd to account for this. But their

Sentiments about it have been various, and the Hypothesis, by which they

have studied to explain it, very different. Some have thought the

Concoction of the Food to be a kind of Elixation; and that the grosser

and more solid Parts being, as it were, boil'd in the Liquid by the Heat

of the Stomach, and the Parts adjacent to it, as the Liver, Spleen, and

Omentum, are by a long and continued Elixation, first render'd more

tender, and then colliquated, and dissolved into minuter Particles, so

as to mix more equally with the Fluid, and with that to make one

Pulpament, or chylous Mass. And _Hippocrates_, tho' he does not plainly

call it an Elixation, yet seems to attribute the Concoction of the Food

to the Heat of the Stomach, as the Cause of it, _Sect. 4. Libro de

salubri victus ratione_. So where he takes notice of the voiding of such

Fæces, as appear to be like the Food that has been eaten; he adds,

_Constat enim, sane ventriculum, ciborum copiam, ut concoquat,

calefacere non posse_. And there are other Passages in the same Book,

from which we may conclude, that he suppos'd the Heat of the Stomach to

be the great Cause of the Digestion of the Food.

There are others that make the Stomach itself to be the great Instrument

of Digestion, but in a different manner: And they suppose it to be

perform'd by an Attrition, as if the Stomach, by those repeated Motions,

which are the necessary Effects of Respiration, when it is distended by

the Aliment, did both rub or grind off some minuter Particles from the

grosser Parts; and by continually agitating the Mass of Food, make those

Parts, which are not contiguous to the Stomach, strike one against

another, and break one another in pieces, until they are all attenuated.

It is evident enough, that the sides of the Stomach do in Expiration

press upon the _Contenta_, so as to oblige, at least some Parts of them,

every time the Muscles of the Abdomen are contracted, to move and shift

their places. So in Inspiration, when the Diaphragm and Liver press upon

the upper part of the Stomach, the Aliment must be moved again. So that

by these reciprocal Motions, that part of the Food which is contiguous

to the Stomach, and moves in a Line parallel to it, must rub against it;

and all the other Parts being moved by such a Compression, as gives them

a different Tendency, it is certain they must be continually striking

one against another. And for Bread, and such things as are made of

Flower, that will be softned and dissolv'd with any common Liquid, that

Agitation of the Stomach which moves them in Respiration, might seem

sufficient to break and dissolve them, when they are sufficiently

moisten'd with a Fluid. Yet this cannot be thought enough to break and

digest Flesh-meat, Fruits, or any other thing that will not be softned

and dissolv'd in Water, or some such Liquid. But although this Motion of

the Aliment, caused by Respiration, does not actually digest it, yet it

has a great and necessary Use in Concoction, and makes all the grosser

Parts, as they are attenuated, mix equally with the Fluid.

Some think that the Bilious Juice; others, that the Spirits are chiefly

concern'd in this Affair. _Galen_, in his Book _de Neutralibus

Facultatibus_, makes it to be the Effect, not of one, but of several

Causes; as a pituitous Juice in the Stomach, the Bile, _&c._ which

appears from what he has said, and the Translator thus render'd: '_Verum

quanto ii (cibi) qui mansi sunt, iis, qui inhæserunt, magis sunt

alterati; tanto etiam his magis ii, qui devorati sunt. Siquidem

incomparabilis erit horum alterationis excessus, si & quæ in ventre est

Pituita & Bilis, & Spiritus, & Calor, & tota Ventris substantia,

æstimentur._'

Some there are that will have the Food to be dissolv'd by a Menstruum,

which is supply'd from the Glands of the Stomach, or some other way: But

those that do so far agree in the General, as to think Concoction is

perform'd by a Dissolvent, do differ in their Notions of the Nature of

the Menstruum: For there are some that suppose it to be an Acid, which

does erode the grosser parts of the Food, and dissolves them in the same

manner as Vinegar, Spirit of Vitriol, or any such-like Acid, will

dissolve even so solid a Body as Iron. And it cannot be deny'd, but that

Oil of Vitriol will dissolve Flesh-meat, and reduce it to a Pulp; but it

is not to be suppos'd, that the Fibres of the Stomach can admit any such

strong and corroding Acid, without something to correct it, but it must

be injur'd in its Tone, and labour under great and extraordinary Pains.

Neither does such a Menstruum, tho' it will digest some things, seem

capable of dissolving so great a Variety of Things as we eat, especially

when a great many of them are of a contrary Nature. Some will have the

Menstruum to be a _nitro-aerius_ Spirit, that is, quick, and very

penetrating, and included in its proper Vehicle; which, being in its own

Nature apt to penetrate the Mass of the Aliment, does diffuse it self

through the Whole, and breaking the Vinculum of the more solid Parts,

does dissolve their Compages. By others, it is thought to be some saline

Juice in the Stomach, by which the Parts of the Aliment are divided and

dissolved, and those which are fit for Nourishment, are volatiliz'd.

_Lastly_, There are some others who reject the Opinions I have already

mention'd, and suppose the Digestion of the Food to be perform'd by the

Benefit of a Ferment; which, when it is mixed with the Aliment, excites

in the Mass an intestine motion; and the different and contrary motions

and tendency of the Parts, making some kind of Collision, gradually

break off Particles from the grosser, and more solid Parts, till they

are so attenuated as to be apt to mix more equally with the Fluid, and

with them to make one soft or chylous Substance. But yet there is not

amongst them an universal Consent, either about the Nature of this

Ferment, or the manner how it is supply'd. For first, some think it to

be the Remains of the Food that was last digested; which having lain

some time in the Stomach, after the rest is carried down into the

Intestines, contracts an Acid, or some other Quality, and is so alter'd,

as to partake of the Nature of a Leaven. And this Leaven being a part of

the Food, which has been already digested, is so soft and liquid as to

be capable of mixing with the Aliment, which is next taken into the

Stomach; and being agitated with it by the repeated Pressures of the

Diaphragm, Liver, and Abdominal Muscles upon the Stomach in Respiration,

does diffuse it self through the whole Mass; and being mixed with it,

like Leaven, or Yest added to new Wort, _&c._ puts it into a State of

Fermentation; and by this Fermentation, or the Expansion of the Ferment,

and the more tenuious Parts, which are first put into motion by it,

those which are more solid, and with which they are intermixed, are

rent, and divided, and so attenuated, as to become a soft and pulpous

matter. And altho' the greatest part of the Food, that is thus broken

and concocted, is by the Contraction of the Fibres of the Stomach

press'd into the Duodenum; yet they do not contract themselves so as to

force out all the Aliment, but leave between the _Rugæ_ or Folds, on the

inside of the Stomach, a sufficient Quantity to be a Leaven to the next

Meal; and so from time to time.

Some have a Notion, That this Ferment, or Principle of Fermentation, is

in the Aliment it self; which being a Congeries of Matter, consisting of

various Parts of a different Nature, is no sooner enclosed in the

Stomach, and digested in the Heat of that, and the adjacent Parts, but

the more spirituous and subtil Particles are put into motion both from

that Warmth, and the difference of their Natures, and enter upon a

Fermentation. And so by their intestine Commotion, and the Violence they

offer to those Parts which oppose the tendency of any of them, they

break and dissolve what is more solid.

Again: Some suppose, that this Ferment is supply'd from the Glands of

the Stomach.

And Lastly, Others, and perhaps with much better Reason, contend for the

Saliva, and make that to be the Ferment, which serves principally for

the Digestion of the Food; which in Mastication being mix'd with our

Aliment, is with that carried down into the Stomach, where the Parts of

it being put into motion by a kindly and agreeable Heat, they do ferment

with, and exagitate first those Parts of the Food which are most apt to

ferment with it, and then both conspire to break and dissolve the

grosser and more stubborn Parts. And _Galen_, in the Book I have

before-mention'd, plainly allows that the _Saliva_ is concern'd in the

business of Concoction, tho' he supposes the Alteration, which is

produc'd by this Juice, to be made in the Mouth, as appears from these

Words: _Quæ (alteratio) in ore agitur mutat quidem id (nutrimentum) in

alteram speciem manifestè, non tamen ad perfectionem transmutat--Qui

mansi sunt cibi primum quidem hac Pituita (oris) imbuunter, & cum ea

miscentur----Itaque majorem mutationem consecuti sunt, quam ii, qui in

vacuis dentium intervallis fuere impacti_.

Now I have given this short Account of the various Opinions of some

Ingenious Men, concerning the manner how Concoction is perform'd; I come

now to propose my own Hypothesis, by which I shall endeavour to explain

it.

In order to the more easie and effectual Digestion of the Food, Nature

has appointed some Parts for the breaking our Aliment, and reducing

whatever is gross into smaller Parts, before it is put upon Digestion:

Others to supply the Ferment, by which it is to be dissolv'd and

concocted, and which, before it comes to be included in the Stomach,

does moisten, and make it more soft, that it may more easily be

penetrated, and broken by those Parts which serve to divide every Morsel

into smaller Pieces, and prevents the Inconvenience and Trouble which

would arise from the Nourishment sticking about or between them, when it

is dry or viscous.

For the breaking of that part of our Food, which is not liquid, Nature

has furnish'd us with Teeth, and those of two sorts: For some are

ordain'd to divide and break off smaller Morsels from a larger Mass;

others are made for the grinding those Morsels into much smaller parts.

The Teeth, which serve to break off Pieces of a convenient Magnitude

from a larger Mass, are of two sorts, accommodated to the Nature of the

Substance which we eat. These are the _Incisores_, and the _Dentes

Canini_. If the Substance, which we have to eat, be not hard, but more

easily penetrated and divided, then the _Incisores_ are capable of

making an Impression upon it, and fix'd firmly enough in the Jaws to

break off that part which they take hold of. But if it be more solid,

and not easily penetrated, nor any Piece without difficulty to be

separated from that Body, whereof it is a part; then we apply the

_Dentes Canini_, or Eye-Teeth, to it, which are not spread, nor have

such an edge as the _Incisores_, but are sharp and pointed like an Awl,

and so do more readily penetrate a Substance that is hard, and which the

_Incisores_ can scarcely make any Impression upon. And as the Parts of a

more solid Body are commonly with more difficulty separated, and there

must be a greater stress put upon those Teeth which pull it into pieces;

so these Teeth are much more firmly fixed in the Jaws than the

_Incisores_, tho' they have but one single Root. Besides, the Position

of all these Teeth is accommodated to their use, as being planted

opposite to the Aperture of the Mouth; so that they may be conveniently

apply'd to the Substance which we have to eat, before it is broken, and

when it is too large to be admitted within the Mouth.

The Teeth which do by a Compression and Attrition reduce the little

Morsels to smaller Parts, are from the manner in which they break the

Aliment, called _Dentes Molares_, because they do, like so many

Mill-stones, grind the Food between them. And that they might be

render'd fit for this purpose, they are made broad at that Extremity,

which stands out of the Gums, by which means they retain some Quantity

of the Food between them every time the lower Jaw is pulled up and

forc'd against the _Maxilla superior_. And as they are broad, so they

are formed with Inequalities and Protuberances; and by the motion of the

lower Jaw, from one side towards the other, they grind what they have

between them into pieces. The Position of these Teeth too is as

convenient as that of the _Incisores_, and the _Dentes Canini_: For

being design'd to break those pieces of our solid Food, which are taken

into the Mouth, and these pieces, when they are compress'd, and mov'd by

the _Dentes Molares_, being apt to fly out of the Mouth, if there were

no Contrivance to prevent it, they are placed beyond the Aperture of the

Mouth, and opposite to the Cheeks, which keep the Food within that

Cavity, and not only so, but press it in between the _Dentes Molares_ on

one side, as the Tongue does on the other, until they have sufficiently

broken and divided it.

At the same time, whilst the _Dentes Molares_ are breaking the Food,

there flows into the Mouth a Salival Juice, which mixes with it, and not

only serves to moisten it, and to render it more apt and easie to be

divided, but seems to be the Ferment, by the Benefit of which the Food

is dissolved and digested. And therefore it is intimately mixed with it,

by the Teeth agitating or stirring them together in Mastication.

This Liquor, which we commonly call the _Saliva_, or Spittle, seems to

be a Composition made of two several Juices, very different in their

Nature: And therefore the several Parts of it are separated by their

proper Glands, and Nature has planted no fewer than four Pair about the

Mouth, which supply the Juices that make the _Saliva_; to wit, the

_Parotides_, and the _Glandulæ Nuckianæ_, the _Glandulæ Maxillares

internæ_, and _Sublinguales_. Whereas if the _Saliva_ were but one more

simple Liquor, a less number of Glands might have been sufficient. At

least there appears no Reason why one of every Pair should disembogue

itself into the Mouth so very near to the Orifice, by which a Gland of

some other Pair throws in its Juice; and they are not rather all planted

at more equal distances from one another, so to flow in upon every part

of the Aliment at the same time.

Not that I suppose, as there are four Pair of salivatory Glands, so

there are four sorts of Juices supply'd from them, to make the _Saliva_;

but, as I hinted before, that there are only two different Juices that

constitute it. And these are not only sufficient, but more proper to

excite and secure that Fermentation, which is necessary to Concoction.

For we find that most of those Fermentations, which arise upon Mixtures

made for Experiments, are produced from the mixture of two things; and

it is not so easie to find out three or four such Liquors of a different

Nature, as will, upon the mixtion of them all, produce a Fermentation,

and from the omission of any one of them discover no Discord or

Disposition to ferment: Besides, it is certain that two do better secure

the End, which Nature designs. For, if there were three or four

different Juices, of which the _Saliva_ naturally consists, these must

all have their proper Qualities preserved to them, or else the

Fermentation, which should arise between them, will not necessarily

follow upon their mixture; and it is certain, that there would be more

Danger, that one of three or four should be deprived of its Natural

Quality, than one of two.

What Nature these two Juices are of, I do not pretend positively to

determine; but so far as I have been able to make my Conjectures about

it from Experiments, I do think one of them to be an acid Juice; the

other an oleaginous Liquor, something like Oil of Turpentine. For

amongst the many Experiments I have made, there was no one that gave me

so much Satisfaction, as that which I made with Oil of Turpentine, and

Oil of Vitriol, though I try'd several other things, that will produce a

Fermentation upon their Mixture. And it was for this Reason, that I made

the Experiment with Oil of Turpentine and the other Oil.

I took a piece of raw Flesh, and having cut it into pieces, but much

larger than what our more solid Food is reduc'd to by due Mastication, I

mix'd some Crums of Bread with it, then I pour'd in the Oil of

Turpentine to them, and upon that the Oil of Vitriol; and having shak'd

them together, I digested them about four Hours in _Balneo Mariæ_, and

then shaking them again in the Glass, I found the Meat dissolv'd, and

they all became a thickish Pulp. I could not but take notice, that Oil

of Camphire (though it does not otherwise seem much different in its

Nature from Oil of Turpentine) and Oil of Vitriol, which upon mixture

will produce an Effervescence as well as the Oil of Turpentine and Oil

of Vitriol, yet did not touch the Meat, upon which I poured them, so as

in the least to dissolve them. I cannot deny but that an Acid, and a

Solution of Salt of Tartar, did dissolve some part of the Flesh-meat,

which I mix'd them with, but yet neither so soon, nor so perfectly as

the two forementioned Oils. And I do the rather think one of those

Juices, which constitute the _Saliva_, to be of the Nature of Oil of

Turpentine, than of a fix'd Salt, because it will correct and temper

even Oil of Vitriol, so as to render it more tolerable to the Fibres of

the Stomach. Not that I suppose the acid part of the _Saliva_ to come

near to the Acidity of Oil of Vitriol. For though, when they are mix'd,

they will make a Liquor that may not be injurious to the Stomach; yet

the acid Juice, if it were so corrosive as Oil of Vitriol, would

certainly be injurious and painful to the Salivatory Ducts, which convey

it to the Mouth before it is mix'd with the oleaginous Liquor. But I

only say it is an Acid, and in some degree approaches to the Nature of

that Oil. And Nature, which can much better adapt several Causes for the

Production of such an Effect than Art, may attain her End by a more

temperate Acid; though, at the same time, we may be able to make some

probable and true Conjectures about the Nature of those Causes from

Experiments.

It being most reasonable to suppose, that there are but two sorts of

Juices, of a different Quality, that make the _Saliva_, I do conceive,

that four of the eight Salivatory Glands, or two Pair of the four, do

supply one of these Juices, and the other four Glands the other. And

this seems to be a very good Reason, why they are so planted, and the

Orifice of their Ducts so order'd, that the Juice, which is supply'd by

one Gland, is discharg'd into the Mouth, very near to the Orifice, by

which the Juice of a different Nature is transmitted from another, so

that they must necessarily meet and mix together. Thus the _Glandulæ

Nuckianæ_, and _Parotides_, throw in two different Juices by Orifices,

which open into the Mouth very near to one another; and the _Glandulæ

Maxillares internæ_, and _Sublinguales_, do below supply the same kind

of Juices by Orifices, that open so near to one another as to secure the

mixture of the two different Juices.

These Glands, I say, do between them afford two divers sorts of Liquors,

of such a Nature as are apt to ferment upon their first Mixture, but

perhaps more considerably when they come to be digested by the Heat of

the Stomach. So that the Colluctation, or Fermentation, which attenuates

and concocts the Food in the Stomach, does not ordinarily arise between

the Aliment and the _Saliva_, but between the several Parts of the

_Saliva_ it self. And indeed, if the _Saliva_ did not consist of two

Juices, whose Nature is in such a manner different, as to render them

apt to ferment upon their mixture, it would be very hard to conceive how

it should so readily and indifferently serve for the Digestion of all

Eatables; how it should ferment with, and dissolve so great a variety of

Things, not only of a different, but of a contrary Nature; how it should

ferment with Acids as well as Alkalies, digest things that are cold, as

well as hot or temperate; some things that are salt, others that are

insipid, bitter and sweet, mucilaginous, oily, _&c._ But if we suppose,

that the Fermentation, which serves for the Digestion of the Food,

arises from a peculiar difference in the Nature of two Juices, which

constitute the _Saliva_, it will be easie to give a rational Account of

our Concoction of innumerable things of a different Nature. And this

seems to be as effectual, and a more certain way to attenuate and

dissolve the grosser Parts of our Food, than if the Fermentation were

made only between the _Saliva_ and the Aliment: Besides, the _Saliva_

seems to discover a Fermentation upon the mixture of its constituent

Juices, even at those times when we do not actually eat; for it is

always attended with Bubbles, and a Froth, when it has not been at all

agitated in the Mouth, and many of those Bubbles will remain for some

considerable time after we have spit it out.

Nature therefore having appointed the _Saliva_ for the digestion of the

Food, has taken care that it shall be thrown in upon the Aliment on

every side. Thus the _Glandulæ Nuckianæ_, and the _Parotides_, supply

their Juices to that part of the Food, which lies on the outside of the

Gums, between the Cheeks and the Teeth, and the _Glandulæ Maxillares

internæ_, and _Sublinguales_, do bestow their Liquor upon the Meat,

which is within the Teeth and Gums. Neither has she had a Regard only to

that Supply, which is due to all the parts of our Food, but likewise to

the mixture of the two different Juices of the _Saliva_, which is

necessary to its Fermentation. And therefore, as I have already

observ'd, the Orifices of the Ducts, which belong to one sort of Glands,

are placed near the Aperture of a Duct, which conveys a Juice from one

of the other Glands. So the Ducts of the _Glandulæ Nuckianæ_, and the

_Ductus Stenoniani_, do on each side open into the Mouth, near one

another; and the salivatory Ducts of the _Glandulæ Sublinguales_, and

the _Maxillares internæ_, though they have distinct Orifices, empty

themselves under the same _Papillæ_, and the Juices, which are supply'd

by them, meet there, and flow into the Mouth together.

The several Parts of the _Saliva_ being discharg'd into the Mouth in

such a manner as to meet and begin a Fermentation, the _Saliva_ does,

partly as it is agitated, with the Food by the Teeth, and some other

parts of the Mouth; partly by its own Fluidity, insinuate it self into,

and mixes with the Food, and not only moistens and softens it, but

excites the Fermentation, which is to dissolve it. And when the Aliment

is thus mix'd with the _Saliva_, which serves to ferment the whole Mass,

it is then to be convey'd into the Stomach, that great digestive Vessel

of the Body, where the Fermentation is not only continued, but improved.

The Nourishment being convey'd into the Cavity of the Stomach, is there

kept for some time in a digestive Heat, all which time it is under a

Fermentation, produc'd by the different Parts or Juices of the _Saliva_,

which are mix'd with it; which Fermentation does first agitate the more

tenuious or subtil parts of the Food, and puts them into motion, and so

with the Fermentation of its own, and those Alimentary Parts, which it

first communicates a Motion to, improved by the Heat of the Stomach, the

_Saliva_ must necessarily act upon the grosser Parts. For the intestine

Motion, which is excited in the Mass, does not give the Particles, which

are fermented, the same Tendency, but what is so various and confus'd,

that they must inevitably strike not only one against another, but

against those which are more gross, so as to attenuate them, sometimes

by a Collision, which strikes off smaller Particles from the larger

Parts; sometimes by a Compression, when the Particles which are in

Motion, happen to strike directly against any grosser Part, on every

side of it, sometimes by a kind of Explosion. For without doubt the

_Saliva_, which is fluid, insinuates it self into the Interstices of the

more crass Parts of the Aliment, and whatever is agitated and expanded

in those Interstices, requiring a larger space for the Freedom of its

Motion, and offering a Violence to every thing that opposes its

Tendency, will, like Gun-powder included in a Shell, force its way out,

and tear to pieces that Matter, which does endeavour to confine it.

Thus the grosser Parts are broken and divided, until they are at last so

far attenuated as to mix more equally with the Fluid, and with them to

make one Pulp or Chylous Mass. And although I do not apprehend how the

Stomach should by its reciprocal Motions in Inspiration and Expiration,

be able to break and attenuate any Matter, that will not be softned and

dissolved by Agitation in a Liquid; yet it is certain that these

Motions, caused by the Diaphragm and Abdominal Muscles in Respiration,

do make those Parts, which are broken off, as they are dissolv'd, mix

intimately with the more Liquid; as the Meat which I digested with Oil

of Turpentine, and Oil of Vitriol, did by Agitation mix more equally

with the Oils, and became a Pulpament.

As the Juices, which constitute the _Saliva_, do ferment upon their

mixture, so it is probable, that from their Mixture and Fermentation

there results such a _Tertium quid_, as is apt to ferment with the Bile.

And therefore, when the Aliment has been under the Fermentation, excited

by the _Saliva_, a sufficient time, it is then thrown into the

_Duodenum_, where it meets with the bilious Juice, which flows into that

Intestine from the Liver, from which a new Fermentation seems to begin;

and the Commotion of the Parts of the Aliment being still continued,

does carry on the Business of Digestion until the Food is perfectly

concocted: Though it is probable, that this new Fermentation serves not

only for the more perfect Digestion of the Food, but likewise for the

Separation of the Chyle from the feculent Parts.

Neither do I by a random Guess, and an ungrounded Conjecture, suppose

that from the Mixture and Fermentation of the two Juices, which

constitute the _Saliva_, there results a Matter, which is apt to ferment

with the Bile. But to me the Notion seem'd to be confirmed by an

Experiment that I made. For considering with my self, that the Bile is

generally allow'd to have much of a saponary Nature, I made a Solution

of Soap in fair Water, and mix'd it with the Oils of Turpentine and

Vitriol first put together, and from their Mixture I observ'd a very

easie and gentle Fermentation, which continued for a considerable time.

_A Discourse concerning some Influence of _Respiration_ on the _Motion_

of the _Heart_, hitherto unobserved. By _J. Drake_, M. D. F. R. S._

Tho' divers accurate Treatises of the _Heart_, and its Action, have been

written by Learned Men of several Nations, especially by two of our own

Country; the Great Dr. _Harvey_, to whose happy Sagacity this Nation

owes the Glory of the Invention of the _Circulation_ of the _Blood_; and

the incomparable Dr. _Lower_, to whom we are beholden for a compleat

Display of the _Mechanical Structure_ of the _Heart_, and a most

ingenious Rationale of its Action. Yet there remain several Doubts and

Difficulties about it (in my Opinion) not sufficiently accounted for;

towards the resolving some of which, I shall offer what my own Thoughts

have suggested to me, and leave it to the Consideration of the Reader.

The Learned Dr. _Lower_ (whose accurate Piece on this Argument will

insure his Reputation so long as Physical Knowledge shall last in

esteem) has so well accounted for the _Systole_, or Contraction of the

Heart, from the _Mechanical_ Structure of it, that he seems almost to

have exhausted the Subject; and had he been as happy in discovering the

true cause of the _Diastole_, he had left little room for the Industry

and Sagacity of others about this _Viscus_.

But having judiciously and solidly explain'd the _Systole_, he contents

himself to ascribe the _Diastole_ to a motion of _Restitution_, which

account gives me no Satisfaction: Because the _Systole_ being the

proper, and (as himself confesses) the only motion of the Heart, a State

of _Contraction_ seems to be the natural State, and consequently without

External Violence, it shou'd have no _Diastole_ at all.

This will appear more plain, if we consider the Circumstances of it, and

its Motion, as a Muscle, with respect to other Muscles. That Contraction

is the proper Action, and State of all Muscles, is evident from

Experience of Fact, as well as Reason. For, if any Muscle be freed from

the power of its _Antagonist_, it is immediately _contracted_, and is

not by any Action of the Will, or Spirits, to be reduced to a State of

_Dilatation_. Thus, if the _Musculi Flexores_ of any Joint be divided,

the _Extensores_ of that Joint being by that means free'd from the

contrary Action of their _Antagonists_, that Joint is immediately

extended without any consent of the Will, and in that State it remains;

and so _Vice versa_, if the _Extensores_ be divided. From whence it is

plain, that the Muscles have no restitutive Motion, but what they derive

from the Action of their _Antagonists_, by which they are balanc'd. Thus

likewise the _Sphincters_ of the _Gula_, _Anus_ and _Vesica_, having no

proper _Antagonists_, are always in a State of Contraction, and suffer

nothing to pass them, but what is forced through them by the contrary

Action of some stronger Muscles, which, though not properly to be call'd

_Antagonists_, yet on all necessary Occasions perform the Office of such.

That the Heart is a Muscle, furnish'd and instructed for Motion like

other Muscles, is (in my Opinion at least) demonstrated beyond

Contradiction by Dr. _Lower_ and others. And, as it is a _Solitary_

Muscle without any proper _Antagonist_, and not directly under the power

of the Will, nor exercising _Voluntary_ Motion, it approaches nearest to

the _Sphincter_ kind, which only has these Conditions in common with it.

But in constant and regular Alternations of Contraction and Dilatation,

it differs exceedingly from all the Muscles of the Body.

This _reciprocal Æstus_ of the Heart has given the Learned abundance of

trouble; who, finding nothing peculiar in the Structure, which shou'd

necessarily occasion it, nor any _Antagonist_, whose re-action should

produce it, have been extreamly perplex'd to find out the cause of it.

But passing over the various Opinions of Authors, to avoid being

tedious, I shall take notice here only of the very Learned Dr.

_Lower_'s, in whose Account of the _Systole_, however solid and

ingenious, I observe something deficient, and whose _Hypothesis_ of the

_Diastole_ I think to be precarious and false.

This Excellent Author, having by sound Arguments drawn from the

Structure and Mechanism of the Heart, establish'd the Certainty of its

_Muscular Motion_, rests satisfied, without taking notice of any

Assistance, that the Heart receives from any other Part, except from the

Brain, by the means of the eight pair of Nerves.

[Sidenote: _Part_ 2_d_. _Prop._ 67. _Prop._ 73.]

[Sidenote: _Prop._ 76.]

The Accurate _Borellus_, in his _Oeconomia Animalis_, computes the

_Motive_ Power of the _Machine_ of the Heart to be equal to, or to

surmount that of a Weight of 3000_l._ The _Obstacles_ to the Motion of

the Blood thro' the _Arteries_ he esteems equivalent to 180,000_l._

which is 60 times as much as he rates the Force of the Heart at. Then

deducting 45,000_l._ for the adventitious Help of the _Muscular Elastic

Coat_ of the _Arteries_, he leaves the Heart with a Force of 3,000_l._

to overcome a resistance of 135,000_l._ that is, with 1, to remove 45.

This stupendous Effect he contents himself to ascribe to the _Energy_ of

_Percussion_. But, had he proceeded in his Calculation to the Veins,

which he allows to contain constantly a quantity of Blood, quadruple to

the Contents of the Arteries, and to which this _Energy_ of _Percussion_

does either not reach at all, or but very languidly, he might probably

have seen a necessity for some other Expedient to remove so insuperable

a Difficulty.

But not to insist rigorously on the Exactness of this Calculation,

(though the great Abilities of the Author in this way, and his Ingenuity

and Modesty, are a sufficient Warrant for the Accuracy of his

Computations, and the Fidelity of his Accounts) we may allow a much

greater Deduction, than would be justifiable, without lessening the

Difficulty. But this Account I have taken notice of purely for the sake

of the Calculation, which may be of use in the Sequel; the account it

self being in other respects more defective than Dr. _Lower_'s, to which

we will return.

The Doctor, notwithstanding his great Sagacity, appears (to me) to have

overlook'd something of very great moment, and importance in the

explication of the Action of the Heart. For, tho' it should be granted,

that the _Muscular Fibres_ of the Heart acted by the Nerves, are the

immediate Instruments of its _Constriction_ or _Systole_, yet it must

not be denied, that the _Intercostal_ Muscles and _Diaphragm_ are of

great service to aid and facilitate this Contraction, by opening a

Passage for the Blood through the Lungs, which denied would be an

invincible Obstacle.

Neither do they promote it that way only. The manner how they farther

assist the Heart in its Contraction, will appear manifestly, if we

consider the different Posture, Situation, and Capacity of the

Blood-Vessels of the Lungs in the several times of _Elevation_ and

_Depression_ of the _Costæ_.

The _Pulmonary_ Artery rises from the _right_ Ventricle of the Heart,

and runs in one Trunk, till it comes to the _Aspera Arteria_, where it

is divided, and sends a Branch along with each Division of the _Aspera

Arteria_, according to all the minutest Subdivisions, of which it is

likewise subdivided, accompanying all the _Bronchi_, in their whole

progress through the Lungs.

The _Pulmonary_ Vein, which empties itself into the _Left_ Ventricle of

the Heart, spreads it self on the _Aspera Arteria_ and _Bronchi_, in the

same manner that the Artery does.

The necessary confluence of this Disposition if, that this Artery and

Vein being co-extended with, and fasten'd to the _Bronchi_, must needs

suffer such alteration of _Superficial_ Dimensions, as the _Bronchi_ do

in the _Elevation_ or _Depression_ of the _Costæ_.

While the Ribs are in a State of _Depression_ (whether before Commerce

with the External Air or after) the _Annular Cartilages_ of the

_Bronchi_ shrink one into another, and by that means their _Dimensions_

are exceedingly contracted. In conformity to this condition of the

_Bronchi_, the _Pulmonary_ Artery and Vein must likewise, either by

means of their _Muscular_ Coats, contract themselves to the same

_Dimensions_, or lye in _Folds_ or _Corrugations_, which is less

probable.

On the other hand, when the Ribs are elevated, and the _Diaphragm_ bears

downward, the Air rushing into the Lungs, shoots out the _Cartilaginous_

Rings, and _divaricates_ the Branches of the _Trachea_, and by them

extends and divaricates the several Divisions of the _Pulmonary_ Artery

and Veins, and thereby lengthens and enlarges their Cavities.

This enlargement of their Cavities is very considerable, not only upon

the score of the addition, which they receive in length thereby, but

also upon the account of their _Divarication_. For whereas, when the

Ribs are depress'd, and the Lungs subside, the Blood-vessels are not

only contracted, (as I have already observ'd) but their Branches,

which are exceeding numerous, approach one another, and lie in

_juxta-position_, by which their Cavities are very much compress'd and

streighten'd: When the Ribs are elevated, and the Lungs turgid with Air,

not only the Fibres, by which their Coats in the opposite state were

contracted, are extended; but those innumerable Vessels, which lying

before in lines almost parallel upon one another, compress'd one

another, making an _acute_ Angle at their Junctures, are divaricated and

separated from each other, and make an _obtuse_, whereby their Channels

are widened.

Thus a passage is open'd to the Blood, from the _Right_ Ventricle of the

Heart to the _Left_, through the Lungs, to which it could not otherwise

pass; and the opposition, which the Blood contain'd in that Ventricle,

must otherwise necessarily have made to its Constriction, is taken off,

and the _Systole_ thereby facilitated.

Nor is that all. For the _Diastole_ being caus'd (as I shall in the

Sequel shew) by the force of the Blood rushing into the Ventricles, this

Ampliation and Extension of the _Pulmonary_ Artery is a sort of _Check_

or _Counterpoise_ to it, and prevents an endeavour towards two contrary

Actions at once, which must necessarily frustrate both. For the Heart

being a _Springy_, _Compressible_ Body, whose proper Action, which is

Contraction, depends on the influx of certain Fluids into its Fibers, or

Substance; and containing besides a Fluid in its _Ventricles_, or great

Cavities, in one of which is the Mouth of this Artery, the action of

this Vessel must in great measure resemble that of a _Syringe_, whose

extremity is immers'd in Water, the Enlargement or Expansion of the

Chanels of the Artery answering the drawing of the _Embolum_, as the

constrictive motion of the Muscle of the Heart does the pressure of the

_Atmosphere_ upon the _Surface_ of the Water, the one making way for the

fluid, and the other forcing it to follow, where the resistance is

least. In this Sense we may allow a sort of Attraction to the

_Pulmonary_-Artery, depending wholly upon the Action of the

_Intercostal_ Muscles and _Diaphragm_, which we must therefore confess

to be very serviceable and instrumental in promoting the _Systole_ of

the Heart.

But if the Learned Author be deficient in his Account of the _Systole_;

that is, if he has not observ'd all the Mechanism and Contrivance of

Nature for the Contraction of the Heart; much less sufficiently has he

accounted for the _Diastole_, or Dilatation of it, which he ascribes to

a motion of _Restitution_ of the over-strain'd Fibres, which yet he

confesses are made for _Constriction_ only. 'Tis true, he immediately

after joins the _Influx_ of the _Blood_ as a concurrent Cause; but from

the slight notice that he takes of it, 'tis plain, that he did not so

much as dream of any great share it had in that Action. His Words are

these:

[Sidenote: _De Corde, Pag. 75._]

_Quin & (ut obiter hoc moneam) omnis motus contractione perficiatur, &

Cordis Fibræ ad constrictionem solum factæ sint, apparet quoque Cordis

motum _totum_ in _Systole_ positum esse; cumque Fibræ ultra tonum suum

in omni constrictione eius tendantur, idcirco ubi nixus iste absolvitur,

motu quasi _restitutionis_ Cor iterum relaxatur, & sanguine à Venis

_influente_ rursus distenditur; à _nullo_ enim cordis motu, nisi

_tensionem suam remittente_, & ab _irruente_ sanguine _Diastole_ ejus

libratis adeo viribus succedit._

I have transcrib'd the intire Paragraph, because it contains his whole

_Hypothesis_ of the _Diastole_, and all the notice that he takes of it

through his whole Work. But how slender soever this may prove, it is the

most substantial that I have any where met with, except a late one of

Mr. _Cowper_, which is properly an Improvement of this, and shall be

consider'd in the Sequel.

But if Contraction be the sole Action of these Fibres (as this Great Man

confesses it to be) and as indeed it is of all _Muscular_ Fibres, I

wonder how so judicious a Writer came to slip into such an Absurdity, as

to call their Distention (vulgarly but improperly call'd Relaxation) a

Motion of _Restitution_. For from the Nature of those Fibres, and their

disposition in the Structure of the Heart, the natural State of the

Heart appears manifestly to be _Tonical_, and its Dilatation a State of

Violence; and consequently, the Constriction is the _true_ motion of

_Restitution_, and the State to which it will _spontaneously_ return,

when the Force is taken off, which is the work of the _Intercostal_

Muscles and _Diaphragm_.

Thus we are left still to seek for the true Cause of the _Diastole_,

which seems to me to be the main and most difficult _Phænomenon_,

relating to the Heart and the Circulation of the Blood. But in Mr.

_Cowper_'s ingenious _Introduction_ to his _Anatomy of Humane Bodies_, I

find the Share which Dr. _Lower_ hints the Blood to have in that Action,

further prosecuted, and improved into the main Instrument of the

Dilatation of the Heart, wherein I agree intirely with him. But as to

the manner, and reasons of its being so very instrumental, I can't be so

perfectly of his mind.

_The Heart (_says this accurate Anatomist_) of an Animal bears a great

Analogy to the Pendulums of those Artificial Automata, Clocks and

Watches, whilst its motion is performed like that of other Muscles, the

Blood doing the Office of a _Pondus_._

This Explication, being but a Simile without a distinct application to

Particulars, is beside so very short, that I can at best but give a

conjecture at the meaning; which if I mistake, I shall deserve to be

excused, and expect to be better inform'd.

By the _Bloods_ doing the Office of a _Pondus_, I suppose he means, that

the Blood contributes in the same manner to the motion of the Heart, as

the _Weights_ do to that of the _Pendulum_ of a _Clock_. If so, the

Blood, according to him, must be the Instrument of _Constriction_; and

_Dilatation_ must be the _Natural_ State, or _Spontaneous_ Motion, to

which it wou'd, when under no violence, return; the contrary of which, I

presume, will appear e're I have done.

But if he means, that the _Blood_ in its reflux, by _gravitating_ on the

_Auricles_ and _Ventricles_, dilates and expands 'em, acting therein as

a _Counterpoise_ to its contractions as a Muscle, I cou'd wish his

Design had not bound him up to so narrow a compass, and that he had

given us an explication at large of so abstruse and so important a

_Phænomenon_: Because the _Specifick Gravity_ of the Blood seems to me a

cause by no means alone adequate to the effect, which it is here

suppos'd to produce.

For, if the Blood acts only as a _weight_ by meer _gravitation_, then

that part of it only which descends from the Parts above the Heart can

be employ'd in that Action. This at the largest computation can't amount

to Five pound weight, and must, according to the computation of

_Borellus_, force a Machine, that is able to overcome a resistance of

135,000_l._ I leave every Man to deduct what he shall upon examination

find reasonably to be deducted, and yet shall rest secure, that it is

not to be effected in the least with so small a Weight.

But neither does the _Refluent_ Blood gravitate in any such proportion,

as I have here assign'd. For to make a true estimate of its

_Gravitation_, we must consider the Circumstances of the Liquor suppos'd

to gravitate; in which it very much resembles Water inclos'd in a

recurve Tube, of which, if the length of the two Legs be equal, it may

be suspended in the Air full of Water, with the Extremities downwards,

without losing a drop, although the _Diameter_ of those Legs should be

very unequal. The Case of the Arteries and Veins is pretty near a

parallel to a Tube, so fill'd and inverted. For, if the Arteries and

Veins be continued Tubes, (as by the Microscope they are made to appear)

then supposing their contents to have no other determination of motion,

than their own weight wou'd give them, the contain'd Fluids must be

Counterpoises to each other. For the Veins and Arteries being join'd at

the smaller Extremities, and the larger of both terminating in the

same parallel Line, it is impossible, according to the Laws of

_Hydrostaticks_, that the contents of either shou'd overbalance t'other.

How far then must it fall short of forcing the natural Power and

Resistance of so strong a Muscle as the Heart, by meer Gravitation?

The Blood indeed has a _Progressive_ Motion through its Vessels, wherein

it differs from Water, in a recurve Tube, in the Experiment

above-stated. But, if the natural Gravitation of the Blood contributes

nothing to the Dilatation of the Heart, this progressive Motion will not

be found much more sufficient. For, as this Motion is deriv'd intirely

from the Heart's Constriction (as all Accounts hitherto derive it) cou'd

the Blood be suppos'd to re-act upon it by the Heart, with all the force

first impress'd upon it by the Heart, it would be insufficient, unless

we will suppose the _Force communicated_ to be superiour to the _Power

Communicant_, which is absurd.

But when the just and necessary Deductions for the Impediments, which

the Blood meets with in its Progress through the Vessels, shall be made,

the remaining Force will be found so exceeding weak, that to prop the

Blood through the Veins may be a task alone too great for so small a

Power, without charging it with the additional difficulty of forcing the

Muscle of the Heart.

_Alphonsus Borellus_, after a great deal of solemn pains taken to shew

his Care and Exactness, and to possess his Reader of the Truth of his

Calculations, casts up the force of the Heart, and the _Muscular_ Coat

of the Arteries, to be together equal to a weight of 3,750_l._ and

allots them a Resistance equal to 180,000_l._ to overcome which is 45 to

1. To make up for a disproportion, by his own confession, incredible to

those who have not consider'd the Matter as he had done, he flings into

the Scale the additional _Force of Percussion_, which he leaves

_indefinite_, and thinks sufficient to _force any quiescent finite

Resistance whatsoever_.

But as this Account and _Hypothesis_ are part of a Posthumous Work (if a

liberty of Conjecture may be allow'd in so uncertain a Matter,) I shou'd

suspect, that these Papers were left unfinish'd by _Borellus_; or at

least, that in many places the last Hand was never put to them. For

neither in this Place, nor any other of this Work, does he account for

any more than the _Systole_ of the Heart, and the resistance which is

made to the progressive motion of the Blood in the Arteries only. This

alone he found to exceed the Power of the Heart so prodigiously, that he

seems to shuffle it off his Hands with a general and precarious

Solution, as a difficulty that he was desirous to be rid of. For, having

ascrib'd this _stupendous_ (as he himself calls it) effect to the

_Energy of Percussion_, he takes no care to satisfie his Reader any

farther about it, or to refer him, or give him the expectation of

Satisfaction any where else; although he has an express Treatise on the

_Force of Percussion_, which was written preparatory to this, and to

which he frequently refers in other Places of this Work. But what

confirms my suspicion, that this part was intended for a farther Revise

by the Author, is, that he has left the Progress of the Blood through

the Veins, and the _Diastole_ of the Heart, absolutely untouch'd, tho'

they are Difficulties of a much greater magnitude than this, which he

has attempted to account so slightly for: For, in these he is excluded

the benefit of _Percussion_, and has yet a greater resistance to

overcome without it. Omissions of this kind are so unusual with this

Author, where-ever he knows himself to go upon sure grounds, that it is

to me an Argument, that he doubted the sufficience of his _Percussion_,

and reserv'd these important _Phænomena_ for farther Consideration,

without plunging himself into such an Absurdity, as to ascribe to

_Percussion_ any such _Energy_ as to be able (so broken as it returns to

the Heart) by its re-action to force that Power, from whence only it was

at first deriv'd.

Dr. _Lower_, and Mr. _Cowper_, deliver their Opinions of the Cause of

the Dilatation of the Heart so very short, and without any Arguments to

support them, that by exposing them naked, they seem rather to discourse

of it transiently, as Men oblig'd by the Nature of their Subjects to say

something of it, than solicitous to give any full or satisfactory

Account; and therefore I shall proceed no farther upon them here.

But though the _Hypothesis_ of _Borellus_ may, in this Case, be found

precarious or insufficient (a Misfortune that has befallen him in divers

other Particulars) his _Theory_ holds still good. At least it ought to

be allow'd, in justice to his great Abilities and Exactness, till some

Body convicts him of some material Error in his Calculations, which has

not as yet been done by any Body, that I know of.

Supposing then the force of the Heart, and of the _Muscular_ Coat of the

Arteries, as likewise of the resistance, which they must overcome, to be

computed with any degree of accuracy, there remains yet such a

prodigious disproportion to be accounted for, as requires some more

powerful Agent, than any yet assign'd, to make up the deficiency.

What assistance the Heart receives from the action of the _Thorax_

towards the facilitating its Contraction, without which assistance there

cou'd have been no _Systole_, has been already shewn. But neither the

_Intercostal_ Muscles, or _Diaphragm_, which are so instrumental in that

part of its action, can contribute any thing to the _Diastole_; because

they serve only to enlarge the Cavity of the _Thorax_, and thereby to

open a passage to the Blood from the Heart, and promote its Constriction.

Whatever therefore the force is, that dilates the Heart, and is the

cause of the _Diastole_, it must be equal to that of the Heart, the

_Intercostal_ Muscles and _Diaphragm_; to all which it acts as an

Antagonist. I take no notice of the _Serratus Major Anticus_, and other

Muscles; which have an obscure share in the _Elevation_ of the _Costæ_,

because as much may reasonably be deducted upon the account of the

_Obliquus externus Abdominis_, and other Muscles; which having their

Insertions on some of the lower _Ribs_ are as instrumental towards the

_Depression_ of them, and so balance the Account. But the chief use of

these is in violent Respiration: In ordinary Respiration their share is

small.

Such a real Power (which may in the least be suspected of any share in

this Action) is hard, perhaps impossible to be found in the _Machine_ of

any _Animal_ Body; and yet without some such Antagonist, it is as

impossible the Circulation of the Blood should be maintain'd. All the

Engines yet discover'd within the Body, conspire towards the

_Constriction_ of the Heart, which is the _State_ of _Quiescence_, to

which it naturally tends. Yet we find it alternately in a _State_ of

_Violence_, that is, of _Dilatation_; and this upon necessity, because

upon this _Alternation_ depends all Animal Life.

Some sufficient Cause External must therefore be found, to produce this

great _Phænomenon_; which Cause must be either in the _Air_, or

_Atmosphere_, because we have no constant and immediate Commerce with

any other _Mediums_.

Some great Physicians observing this, and that depriv'd by whatsoever

means of Communication with the _external_ Air, we became instantly

extinct, have imagin'd, that in the Act of Inspiration certain purer

parts of the Air, mixed with the Blood in the Lungs, and was convey'd

with it to the Heart, where it nourish'd a sort of _Vital Flame_, which

was the Cause of this reciprocal _Æstus_ of the Heart. Others not quite

so gross, rejecting an _Actual Flame_, have fancied, that these fine

Parts of Air mixing with the Blood in the Ventricles of the Heart,

produc'd an _Effervescence_ which dilated it. But these Fancies have

been long since exploded and condemn'd upon ample Conviction; and 'tis a

Point yet undetermin'd, whether any Air does mix with the Blood at all

in the Lungs, or not.

But supposing, that some Air may insinuate it self into the _Pulmonary_

Vein, it can no other way dilate the Heart than by an Effervescence in

the Left Ventricle, which wou'd not dilate the Right. But this Opinion

is contradicted by _Autopsie_, and too laboriously confuted by others,

to be brought upon the Stage again here.

There remains therefore only the _gross Body_ of the _Atmosphere_ to be

considered, which is undoubtedly the _true Antagonist_ to all those

Muscles, which serve for ordinary Inspiration, and the Constriction of

the Heart. This will appear more evidently, if we consider not only the

Power, but the Necessity of its Action upon _Animal_ Bodies, as well as

the want of other sufficient Agents.

The Heart is a _Solitary_ Muscle of very great strength, and the

_Intercostal_ Muscles and Diaphragm, which likewise have no

_Antagonists_, are a vast additional Force, which must be balanc'd by

the contrary Action of some equivalent Power or other. For, tho' the

Action of the _Intercostal_ Muscles be voluntary, that does not exempt

them from the condition of all other Muscles serving for _voluntary_

motion, which wou'd be in a State of perpetual Contraction,

notwithstanding any Influence of the Will, were it not for the Libration

of _Antagonist_ Muscles. This Libration between other Muscles, is

answer'd by the _Weight_ of the incumbent _Atmosphere_, which presses

upon the _Thorax_ and other parts of the Body. And, as in all other

voluntary Motions the influence of the Will only gives a prevalence to

one of its two Powers before equilibrated, so here it serves to enable

those Muscles to lift up a weight too ponderous for their strength not

so assisted; and therefore as soon as that assistance is withdrawn, the

_Costæ_ are again depress'd by the meer _Gravitation_ of the

_Atmosphere_, which wou'd otherwise remain elevated through the natural

Tendency of those Muscles to Contraction.

This is evidently prov'd from the _Torricellian_ Experiments, and those

made upon Animals in Mr. _Boyle_'s Engine; where, as soon as the Air is

withdrawn, and the _pressure_ thereby taken off, the Intercostal Muscles

and Diaphragm are contracted, and the Ribs elevated in an instant, and

can't by any Power of the Will be made to subside, till the Air is again

let in to bear them forcibly down.

[Sidenote: _De Respirationis Organis & Usu._]

It were scarce worth while to take notice here of a Mistake of the

Learned Dr. _Willis_, were it not for the great Authority of the Man,

which is almost sufficient to keep Error in countenance. The Doctor

having observ'd, that the Fibres of the _External_ and _Internal

Intercostal_ Muscles ran in a contrary order, as it were, decussating

each other, takes occasion from thence to fansie, that there was an

opposition in their Office; and that as the _External_ serv'd to raise

up the Ribs, the _Internal_ drew them down again, forgetting at that

time, That, when a contractile Body is fasten'd at the several ends to

Points unequally moveable, let the Contraction happen in what part or

manner soever, the more moveable Point must be drawn towards the less

moveable: By which Rule, whether _External_ or _Internal Intercostals_

be contracted, the lower Ribs will be forc'd to approach the upper, that

is, be rais'd up.

As in the Elevation of the _Costæ_, the Blood, by the passage that is

open'd for it, is in a manner solicited into the Lungs; so in the

Depression of them, by the subsidence of the Lungs, and the Contraction

of the Blood-Vessels, both which are consequent thereof, the Blood is

forcibly driven, as it were with an _Embolum_, through the Pulmonary

Vein into the Left Ventricle of the Heart. And this, together with the

_general Compression_ of the _Body_ by the _weight_ of the _Atmosphere_,

which surrounds and presses upon the whole Surface of it, is that Power

which causes the Blood to mount in the Veins, after the force impress'd

upon it by the Heart is broken and spent, and which is sufficient to

force the Heart from its natural State to Dilatation.

He that is able to compute the weight of a Column of Air, equal to the

Surface of the whole Body, will readily grant it a power sufficient for

the Effects, which are here ascrib'd to it. And when he considers, that

the Bodies of Animals are compressible Machines, he will find that it

must of necessity affect them in the manner here laid down. But though

our Bodies be entirely compos'd of _Tubuli_, or Vessels fill'd with

Fluids; yet this pressure, how great soever, being equal, cou'd have no

effect upon them, if the superficial Dimensions were not easily

variable; because being compress'd on all parts with the same degree of

Force, the contain'd Fluids cou'd not any where begin to recede, and

make way for the rest to follow, but wou'd remain as fix'd and

immoveable as if they were actually solid. But by the Dilatation of the

_Thorax_, room is made for the Fluids to move, and by the Coarctation of

it, fresh motion is imprest, which is the main Spring whereby the

Circulation is set and kept going.

This reciprocal Dilatation and Contraction of the superficial Dimensions

of the Body, seems so necessary to Animal Life, that there is not any

Animal so imperfect as to want it, at least none to the inward

Structure, of which our Anatomical Discoveries have yet reach'd. For,

tho' most kinds of _Fish_ and _Insects_, want both _moveable_ Ribs and

Lungs, and consequently have no dilatable _Thorax_, yet that want is

made up to 'em by an _Analogous_ Mechanism, answering sufficiently the

Necessities of their Life.

Those Fishes which have no Lungs, have _Gills_, which do the _Office_ of

Lungs, receiving and expelling alternately the Water, whereby the

_Blood-Vessels_ suffer the same alteration of Dimensions, that they do

in the Lungs of more perfect Animals.

The Lungs or _Air-Vessels_ of Insects, are yet exceedingly more

different in Structure, Distribution, and Situation from those of

perfect Animals, than those of Fishes are, and yet in their Use and

Action agree perfectly with both; that is, _receiving_ and _expelling_

the Air, and _varying_ the _Dimensions_ and _Capacities_ of the

_Blood-Vessels_. These having no _Thorax_, or separate Cavity for the

Heart and Air-Vessels, have the latter distributed through the whole

Trunk of their Bodies, by which they communicate with the _External_ Air

through several _Spiracula_ or _Vent-holes_, to which are fasten'd so

many little _Tracheæ_, or Wind-pipes, which thence send their Branches

to all the Muscles and _Viscera_, and seem to accompany the

Blood-Vessels all over the Body, as they do in the Lungs only of perfect

Animals. By this disposition in every _Inspiration_, the whole Body of

these little Animals is inflated, and in every _Expiration_ compress'd;

and consequently the Blood-Vessels must suffer a _Vicissitude_ of

Extension and Contraction, and a greater motion must thereby be

impress'd upon the Fluids contain'd in them, than the Heart, which does

not in those Creatures appear to be Muscular, seems capable of giving.

The only Animal that is exempted from this necessary condition of

_Breathing_, or _receiving_ and _expelling alternately some Fluid_ into

and out of the Body, is a _Fœtus_. But this, while included in the

Womb, has little more than a _vegetative_ Life, and ought scarce to be

reckon'd among the number of _Animals_. For, were it not for that small

share of _Muscular_ Motion, which it exercises in the Womb, it might

without absurdity be accounted for as a Graft upon, or Branch of the

Mother.

[Sidenote: Boyle _of the Elasticity of Air. Pechlinus de Aeris &

Alimenti defectu._]

Concerning the immediate Matter, and Means of Life, and Nutrition,

Authors are not agreed, nor is it the business of this place to

reconcile, or decide their Differences, but to account for the Motion of

the Blood through the Vessels only. In order to this, it will be

necessary to observe, that the Pulsation of the Heart in a _Fœtus_ is

so very weak and obscure, and the Motion of the Blood so extream slow

and languid, as to be scarce, if at all perceivable, as has been

experienced in the Dissection of Puppies before Respiration had. To

produce such a feeble Palpitation, and creeping Motion, no greater force

seems to be required, than may be deriv'd from the Communication between

the Vessels of the Mother and _Fœtus_ in the _Placenta_. I am not

ignorant, that divers very Learned Anatomists (whom the Crowd have

implicitly follow'd) have absolutely rejected all Communication between

these Vessels. But, with submission to Great Authorities, I think they

have acted arbitrarily, and without sufficient Warrant from Reason or

Experiment: For neither are the Arguments which they bring against it

conclusive, nor the Office which they assign to the Umbilical Vessels in

lieu of it, proper, or natural to those Vessels, or the reality of the

Fact made out by any substantial Reasons. Those that reject this

Communication usually do it in favour of one or both of these Opinions,

that the Arteries of the _Uterus_ do deposite a Nutritive Juice, or a

Juice impregnate _with Air_ in the _Placenta_, which is suck'd in by the

_Umbilical_ Vein, and convey'd to the _Fœtus_, for the necessary Uses

of Nutrition and Life. Now those that patronize either of these

Opinions, lead Nature an unnecessary Dance. For if the _Maternal_ Blood

does really contain any such _Nutritious_, or any such necessary _Aerial

Particles_, why shou'd they be separated and extravasated, to be with

difficulty receiv'd into the _Umbilical_ Vein, and again mixt with the

Blood, when they might more easily have been imparted by the plain

simple way of Transfusion from the Arteries of the _Mother_ to the Veins

of the _Fœtus_. And, that this is the course which Nature takes in

this Case, I am perswaded from the easiness and simplicity of the

Method, which readily performs what might be perhaps in vain expected

from the other, and wou'd over and above find them, what they seem to

grope so blindly about for, a first Mover of the Blood in a _Fœtus_.

Those that contend for the conveyance of the _Nutricious_ Juice, through

the _Umbilical_ Vein from the _Placenta_, are forc'd upon two

Difficulties next to Absurdities. For first they are oblig'd to make

this Vein, which, as all other Veins, seems dedicated to the

Re-conveyance of Blood only, the proper and immediate Chanel, thro'

which a very different Liquour is to be carried; and next, to give a

Power of Attraction or Suction to it; because the _Nutricious_ Juice,

which it is thus destin'd to carry, is both viscous and stagnant, and

has neither force to drive, nor subtilty to penetrate, or insinuate it

self into the Capillary Veins; and therefore must be drawn or suck'd as

_Milk_ is from the _Breast_, to which the _Placenta_ and its

_Nutricious_ Juice are by the Favourers of them expresly compar'd. But

if this were the sole use of the _Placenta_, and _Umbilical Vessels_,

why were the Umbilical _Arteries_ sent along with the Vein? Their

business is not to bring any thing back to the _Fœtus_, nor can they

contribute any thing to the benefit of the _Mother_; for the _Uterine_

Arteries bring all to the _Placenta_, the Umbilical Vein carries it to

the _Fœtus_, and the _Uterine_ Veins convey back again the Surcharge

of the _Mother_'s Blood; the Umbilical _Arteries_ only, have nothing to

do, and are superfluous and impertinent, which is contrary to the

constant Practice of Nature. Yet if _Autopsie_ did in the least

countenance this Hypothesis, some Defence might still be made; but we

find in the Umbilical _Vein_ of a _Fœtus_ nothing but _Florid_ Blood,

such as in all probability it received immediately from the _Arteries_

of the _Mother_ without any mixture. And therefore I can't help

concluding, that this Opinion engages its Favourers in some Absurdity,

without Necessity and without Proof.

They that from the _Placenta_ supply the Body of the _Fœtus_ with

_Air_, are as much distress'd as t'other; for they are forc'd to beg the

Question twice, which, even when granted, will not answer their Ends.

First, they suppose, that an intimate mixture or confusion of _Air_ with

the _Blood_, is necessary for the support of Animal Life, a

_Postulatum_, which perhaps the former part of this Discourse may have

render'd unnecessary; and next, that the _Fœtus_ is supply'd with

_Air_ from, and its _Blood_ mix'd with it in the _Placenta_.

But here again they fetch a Compass without necessity or proof. For if a

mixture of _Air_ were necessary to a _Fœtus_, why should it be

separated from the _Mother_'s Blood, and not rather both communicated

together, since it is so much more easie and commodious? But neither

does the _Placenta_ seem to be instructed and provided for the

separation of _Air_, but of a much _grosser Fluid_, destin'd to some

other use, which _Autopsie_ confirms: Yet, were both these Opinions

true, they are however defective, and the Circular Motion of the Blood

unprovided for.

By the way of _Transfusion_, this great Phænomenon is naturally

accounted for, and the Ends, for which the other two Hypotheses were

devis'd, might both be answer'd with more ease. For the _Hysterick_

Arteries transmitting their Blood immediately to the _Umbilical_ Vein,

may very easily transmit such _Nutricious_ Juices or _Aerìal_ Particles,

as are contain'd in the Blood, along with it, without depositing them by

the way. By this means so much of the Impulse of the Mother's Blood is

preserv'd, as suffices to maintain that languid Circulation which a

_Fœtus_ enjoys. For the Blood being driven through the _Arteries_ of

the _Uterus_ into the _Umbilical Vein_, is convey'd directly to the

_Sinus_ of the _Porta_, and thence by a short and direct Passage through

the _Cava_ to the Heart; where passing through the _Foramen Ovale_ to

the _Left_ Ventricle, and through the _Canalis Arteriosus_ from the

_Right_ and _Pulmonary_ Artery, it is all deliver'd without coming at

the _Lungs_ to the _Aorta_, and from thence again by the _Umbilical

Arteries_ to the _Veins_ of the _Uterus_, making a sort of _Epicycle_ to

the main Circulation in the Mother.

As this Opinion is Favour'd by the Structure and Disposition of the

Blood-Vessels on both Parts, so there is nothing in it difficult to be

conceiv'd, or repugnant to Experience. Late Discoveries have made it

appear, that the Arteries and Veins are continu'd Tubes, and that the

latter contain nothing but what they receive from the former, and no

Reason appears why we shou'd think this Method to be varied in the

_Placenta_. On the other hand, if the Arteries of the _Uterus_ were

continued to the Veins of the _same_ part, and those of the _Fœtus_

in like manner, without communicating with each other, their Confluence

in the _Placenta_ seems to be altogether impertinent, and of no use, and

the _Umbilical_ Arteries and Vein fram'd for no other Service or

Purpose, than to give the Blood room for an idle Sally.

Thus the Reasonableness of this old Opinion may be vindicated, but the

Certainty of it rests upon stronger Proof. Mr. _Cowper_, to whose happy

Industry we owe the Confirmation of many ancient Discoveries, and the

Benefit of some new ones, has the Honour to re-establish this old, but

long exploded Truth. For by pouring _Mercury_ into a Branch of the

_Uterine Arterie_ of a _Cow_, that went into one of the _Cotyledones_ of

the _Uterus_, he fill'd those Branches of the _Umbilical_ Veins, which

went from that _Cotyledon_ to the _Navel_ of the _Fœtus_; which, with

a part of the _Uterus_, he keeps prepared by him.

It would be a weak Objection, to alledge, That the Observation and

Experiment being made on the _Uterus_ of a _Cow_, the Inference would

not hold from thence to a _Woman_, the one being _Glanduliferous_, and

the other _Placentiferous_; since every one of these _Cotyledones_, or

_Uterine Glandules_, is in all respects a little _Placenta_, and all the

difference between them is in number, name, and magnitude. Why

_Ruminants_ differ in this Particular from other _Viviparous_ Animals,

is beside the Subject of our present Enquiry. But the great Flux of

Blood, which constantly follows upon drawing the _Placenta_ from Women

(which is frequently so great as to cost them their Lives) is as plain a

demonstration to Reason of the _Continuity_ of the Vessels, as Mr.

_Cowper_'s Experiments is to the Eye.

I have heard it objected by very Learned Men, that if there were such a

_Continuity_ of Vessels, and such _Transfusion_ of Blood, the _Fœtus_

must necessarily perish through loss of Blood, upon the separation of

the _Placenta_ from the _Uterus_; but that, on the contrary, no visible

Flux of Blood does follow while the _Fœtus_ continues wrapt in the

Membrane, in which Condition it may be kept alive some Hours. To this it

may be answer'd, that the Circulation in the _Fœtus_, being deriv'd

from the Mother, may be suppos'd wholly to cease upon the cutting off

the Communication between them, till it is again renew'd more forcibly

by _Respiration_. But if we allow the motion already impress'd upon the

Blood to be sufficient to keep it going a little while; yet it must

needs be so exceeding languid, that the meer resistance of the External

Air must be more than enough to hinder any Efflux of Blood from a

_Fœtus_ before Respiration. How long Life may be preserv'd without an

_actual_ Circulation of the Blood, is a Question not of this place. But

we have been convinc'd by many and notorious Observations and

Experiments, that Life has been recover'd a long time after all tokens

of Respiration, Circulation, or even Life it self, have disappear'd; so

that we can't think the first Solution either impossible or improbable.

I expect to be told, that in the early Days of _Gestation_ in

_Viviparous_ Animals, there is no _Placenta_, or any Adhesion of the

_Umbilical_ Vessels to any part of the _Mother_, and consequently no

such _Transfusion_; and that in _Oviparous_ there is no _continuity_, or

_communication_ of Vessels of any kind, during the whole time of

_Incubation_.

But these Objections carry neither the Weight nor Difficulty along with

them, that they may be suppos'd to do; for in those Days there is

neither _Blood_ or _Blood-Vessels_, and consequently there can be no

_Circulation_ of the _Blood_; and the _Embryo_, of what Species soever,

is no more than a _Vegetable_ at that time; nor does the _Fœtus_ of

any _Viviparous_ Creature enjoy any _Circulation_, or shew any signs of

Animal Life, till after those Vessels, as well as others requisite to

the Circulation, are compleated.

It must be confess'd, that _Oviparous_ Animals are denied the benefit of

this Communication; but that want is sufficiently compensated by a

peculiar Mechanism, which directly answers the ends of _Respiration_,

and the _pressure_ of the _Atmosphere_ upon the _Fœtus_. There is at

the _obtuse_ end of an Egg a small Cavity fill'd with Air, which is the

succedaneous Instrument to the _Respiratory_ Organs. For as soon as the

Contents begin to be warm'd by the _Incubation_ of the Hen, or _any

analogous_ Heat of _Furnace_ or _Dunghill_, the several Humours of the

Egg require a _fermentative_ motion, and the _Air_ contain'd in the

_Cavity_ or _Vesicle_, at the _obtuse_ end of the Egg, is rarefied, and

the Vesicle extended and enlarg'd, and consequently the other Contents

are comprest; to which the _fermentative_ motion naturally resists. But

both Bodies being as well _compressible_ as _dilatable_, and both having

an _expansive_ motion imprest upon them by _Incubation_, the Compression

and Renitency will be mutual, but varied in degree, according as either,

through the variation of Circumstances, shall prevail. By this means, an

Alternation of Compression and Dilatation will be produc'd in both,

answering the _respiratory_ motion, by which a motion will be

communicated, which, as soon as the Organs by which it should be

regulated are compleated, will in the Body of the _Pullus_ be _regular_

and _circulatory_.

_Fabricius_ ab _Aquapendente_, and after him, our Great Dr. _Harvey_,

have assign'd divers Uses to this Cavity or Air Vesicle, the

Extravagance of which have perhaps deterr'd others from enquiring so

much into the Use, as the Importance of it requir'd. But though I can't

agree to that _Perspiration_, _Refrigeration_, and _Respiration_, which

they make it the Instrument of; yet perhaps the _Air_, that was inclos'd

in that _Cavity_, may through the Augmentation of the Body of the

_Pullus_, and its own _Rarefaction_ (which is at last so great as to

occupy half the Shell) break the _Membrane_, which separated it from the

_Pullus_, and thereby give so much _Respiration_ as to form the

_chirping Voice_, which is often heard before the breaking of the Shell,

and with it give an addition of Strength to enable it to break the

Shell. But how it should respire sooner, is to me inconceivable.

There are many Problems of great seeming Difficulty, the Solutions of

which flow naturally from what has been laid down here: But intending to

prosecute this Subject farther, and to treat of the Impediments of

Respiration, and the Consequences of Respiration obstructed or

intermitted, I shall reserve them for that Opportunity, and content my

self here to attempt the _Harveyan_ Problem only, which has given

abundance of Authors so much perplexity.

That incomparable Philosopher enquires, _Why a _Fœtus_, taken out of

the _Uterus_ with the _Membranes_ intire, shall live in Water some Hours

without communication with the _External Air_; whereas if it be taken

out and suffer'd once to breath, it can't afterwards survive a Moment

without the benefit of _Respiration_._

Granting the Fact to be as he has deliver'd it, which yet is not so in

all Cases, the main Difficulty is grounded on a Mistake, which from the

stating of the Question I find this Great Man to have slipt into. For he

thinks, that a _Fœtus_ is sooner suffocated after having once

breath'd, than if it had not breath'd at all, and that by breathing it

had contracted something which render'd it more perishable. _Idem tamen

secundis exutus, (_says he_) si semel _aerem_ intra _Pulmones_

attraxerit, postea ne momentum quidem temporis absque eo durare possit,

sed confestim moriatur._ And presently after, _Siquidem constat,

fœtum, postquam _eum semel_ hauserit, _citius_ suffocari; quam cum ab

_illo prorsus_ accebatur._ The Doctor observing a _Fœtus_ to live

longer without Respiration, and to dispence better with the want of Air

while included in the Membranes intire, than it cou'd afterwards; infers

thence, that the Air does in the first Act of Inspiration impress upon

the Lungs some quality, which renders it ever after more indispensably

necessary. But allowing his Observation, I must yet deny his Inference

to be good: For deprive a _Fœtus_ of means of respiring, and then

take it out of the Membranes, and it shall be as soon suffocated, as if

it had respired before. This proves, that this necessity of intercourse

with the Air, by way of the Lungs, is not the Offspring, but the Parent

of Respiration, and that, that Learned Man was drawn into a Fallacy of

_Non causa pro causa_.

The Reason of this Necessity is the pressure of the External Air upon

the Surface of the Body, from which it was defended by the Interposition

of the Membranes, and the Humours contain'd, which are not so

compressible as the Body of the _Fœtus_ it self. So soon therefore as

the _Fœtus_ is excluded, and expos'd to the immediate contact of the

ambient Atmosphere, the Vessels and all the Cavities of the Body must

necessarily be so compress'd, that the Fluids can't have room for

motion, and consequently the _Fœtus_ could have no Life, if Nature

had not contriv'd by the motion of the _Thorax_ to remove and admit that

pressure alternately, and thereby to impress a motion on the Fluids,

which is the Spring of Life. But this motion of the _Thorax_ being any

way suppress'd, the equal pressure of the Atmosphere on all parts,

occasions a total Cessation of motion, which is Death.

I shall prosecute this Subject no farther now, nor trouble the Reader

with any Apology, for dissenting from those Great Men herein named;

because, I hope, I have done it with Modesty, and all the Respect due to

so great Authorities, and have assign'd nothing which is not Matter of

Fact uncontroverted, or deduc'd from it by plain Mechanical Necessity.

_Some Thoughts and Experiments concerning _Vegetation_. By _John

Woodward_, M. D. of the College of Physicians, and R. S. and

Professor of Physick in _Gresham College_._

The _Ancients_ generally intitled the _Earth_ to the Production of the

_Animals_, _Vegetables_, and _other Bodies_ upon and about it; and that

for that Reason 'twas, that they gave it so frequently the Epithets of

_Parent_ and _Mother_[1]. They were of opinion, that it furnished forth

the _Matter_ whereof _those Bodies_ consist; and receiv'd it all back

again at their Dissolution for the Composure of _others_. Even those who

asserted _four Elements_, supposed that the _Earth_ was the _Matter_

that _constituted_ those Bodies; and that _Water_ and the _rest_, serv'd

only for the _Conveyance_ and _Distribution_ of that _Matter_, in order

to the _forming_ and _composition_ of them. 'Tis true, _Thales_, a

Philosopher of the first Rank in those early Ages, has been thought to

have Sentiments very different from these; but that without just

Grounds, as I think I have sufficiently prov'd in another Paper, which I

am ready to produce.

But though _Antiquity_ thus gave its _Vote_ for _Terrestrial Matter_,

several of the _Moderns_, and some of very _great Name_ too, both _here_

and _abroad_, have gone quite counter, and given _theirs_ in behalf of

_Water_. The _Dignity_ of the _Persons_ that have espoused it, as well

as their _Numbers_, renders this Doctrine very considerable, and well

worth our enquiring into. The great Restorer of _Philosophy_ in this

last Age, my Lord _Bacon_, is of Opinion, _That for Nourishment of

_Vegetables_, the Water is almost all in all; and that the Earth doth

but keep the Plant upright, and save it from over-heat, and

over-cold[2]._ Others there are who are still more express; and assert

Water to be the only Principle or Ingredient of all Natural Things. They

suppose that, I cannot tell by what Process of Nature, Water is

_transmuted_ into _Stones_, into _Plants_, and in brief, all other

Substances whatever. _Helmont_,[3] particularly, and his _Followers_,

are very positive in this; and offer some _Experiments_ to render it

credible. Nay, a very _Extraordinary Person_ of our own _Nation_[4]

tries those _Experiments_ over again; and discovers a great Propensity

to the same Thoughts and Opinion they had; declaring for this

_Transmutation of Water_ into _Plants_ and _other Bodies_, though with

great Modesty and Deference, which was his usual manner.

The _Experiments_ they insist upon are chiefly _two_; the _first_ is,

that _Mint_, and several _other_ _Plants_ prosper and thrive very

greatly in _Water_. The _other_ is this; they take a certain quantity of

_Earth_, and _bake_ it in an _Oven_; then they weigh it, and put it into

an _Earthen Pot_. Having well water'd this _Earth_, they make choice of

some fit _Plant_, which, being first carefully _weigh'd_, they _set_ in

it. There they let it grow, continuing to _water it_ for some time, till

'tis much advanced in _bigness_: Then they take it up; and though the

_Bulk_ and _Weight_ of the _Plant_ be much greater than when _first

set_, yet upon _baking_ the _Earth_, and _weighing_ it, as at first,

they find it little or not at all diminished in _weight_; and therefore

conclude, 'tis not the _Earth_ but _Water_, that nourishes and is

_turn'd_ into the Substance of the _Plant_.

I must confess I cannot see how _this Experiment_ can ever be made with

the _nicety_ and _justness_ that is requisite, in order to _build_ upon

it so _much_ as _these Gentlemen_ do. 'Tis hard to weigh _Earth_ in that

_quantity_, or _Plants_ of the _size_ of those they mention, with any

great _exactness_; or to _bake_ the Earth with that _accuracy_, as to

reduce it _twice_ to just the _same Driness_. But I may wave all this;

for though the _Experiment_ be never so easily practicable, and all the

Accidents of it exactly as they set forth, yet nothing like what they

_infer_ can possibly be concluded from it; unless _Water_, which they so

plentifully bestow upon the _Plant_ in _this Experiment_, be _pure_,

_homogeneous_, and not charged with any _terrestrial Mixture_; for if it

be, the Plant after all may owe its _Growth_ and _Encrease_ intirely to

_that_.

Some _Waters_ are indeed so very _clear_ and _transparent_, that one

would not easily suspect any _terrestrial Matter_ were latent in them;

but they may be _highly saturated_ with such _Matter_, though the Eye be

not presently able to descry or discern it. 'Tis true, _Earth_ is an

_Opake Body_; but it may be so far dissolved, reduced to so extreme

small Particles, and these so _diffused_ through the _watry Mass_, as

not sensibly to impede _Vision_, or render the Water much the less

_diaphanous_. _Silver_ is an _Opake_, and indeed a very _dense Body_;

and yet, if perfectly _dissolved_ in _Spirit_ of _Nitre_, or _Aqua

Fortis_, that is _rectified_ and thorowly _fine_, it does not _darken_

the _Menstruum_, or render it less _pellucid_ than before[5]. And other

Instances there are, that oftentimes _great quantities_ of _Opake

Matter_ are sustain'd in _Fluids_, without considerably striking the

_Eye_, or being perceiv'd by it. So that were there _Water_ any where

found so _pure_, that the quickest Eye could discover in it no

_terrestrial Intermixture_; that would be far short of a _Proof_, that

in reality there was _none_.