In origin and early development the ovary and testis are identical. The
gonad and mesonephros or primitive kidney are developed from the
urogenital fold. The gonad first forms as a medio-ventral thickening of
the fold, which gradually expands until it becomes attached by a mere
stalk. At first, the gland is made up merely of a superficial epithelial
layer, and an inner epithelial mass, or epithelial nucleus. In the
process of development, large primordial germ cells migrate from the
entoderm of the future intestinal canal, and pass through the stalk to
the gonad. In the case of the male gonad, seminiferous tubules are very
difficult to make out in embryos smaller than 24 millimeters. Then they
suddenly differentiate out as solid cords of germ cells, while the
connective tissue grows in around them. These connective tissue sheaths
unite at the center of the organ to form the anlage of the mediastinum
testis. The testicular tubules unite and converge toward the hilus,
there to meet the anlage of the rete. At the mesonephric end of the
testis, the rete first appears as a collection of cells, differentiating
out from the inner epithelial mass of the gonad. These cells gradually
grow out to meet the collecting portions of the mesonephric tubules on
the one hand, and the seminiferous tubules on the other. The rete is
represented as cords of cells at first, which in forty millimeter
embryos hollow out to form tubules.
The mesonephros, or primitive kidney, early starts to degenerate
cranio-caudally,—the tubules becoming separated into a cranial and
caudal group. The collecting and secretory parts of the cranial group
separate, the collecting tubules growing out to meet the rete with which
they unite to form the efferent ductules of the epididymis. The caudal
group of tubules is vestigial and becomes the paradidymis. The
mesonephric duct becomes the vas deferens, connecting as it does with
the tubules of the epididymis, and emptying into the urethra at Müller’s
tubercle or, as it later becomes, the colliculus seminalis.
The seminal vesicles arise as hollow saccules from the dorsal wall of
the mesonephric duct just as it empties into the urethra. The prostate
develops as an outgrowth of the dorsal urethra just posterior to
Müller’s tubercle. The bulbo-urethral glands appear as solid, paired,
epithelial outgrowths from the entoderm of the urogenital sinus.
Müller’s duct, at first a solid tube growing from the anterior part of
the mesonephros, and ending at Müller’s tubercle, becomes a hollow tube,
and in the female forms the entire genital tract except for the gonad
and the lower part of the vagina. In the male, the anterior part remains
as the vestigial appendix testis, and the posterior part, as the vagina
masculina. Ellenberger states, however, that this embryonic structure is
very seldom seen in the mature bull.
The _Male Reproductive Organs_ include the penis and testes, together
with the excretory passages which connect the testes with the urethral
canal. These excretory ducts include the epididymis, vas deferens, and
seminal vesicles. Posterior to their termination in the urethra, there
are connected the ducts of the prostate gland and the bulbo-urethral or
Cowper’s glands.
TESTES: The testicles of the bull are relatively large. Varying with the
size and age of the animal they measure from fourteen to seventeen
centimeters in length, including the epididymis, and from six to eight
centimeters in diameter. Each testicle is enclosed within a serous sac,
the tunica vaginalis, whose visceral layer is very intimately fused with
the underlying covering of the organ, the tunica albuginea. The tunica
albuginea is quite thin and consists of connective tissue which is rich
in elastic fibres. Muscular tissue is not present as it is in the case
of many mammals. Inside the tunica, and closely attached to, though
separated from, the parenchyma by a thin layer of connective tissue, is
a layer of very loose connective tissue, which because of its rich
supply of blood vessels is termed the tunica vasculosa. The parenchyma
is of a yellowish gray color, and of a rather soft consistency. It is
made up of the seminiferous tubules, rete, and the connective tissue
stroma, the mediastinum testis. On section, the mediastinum appears as
the center or axis of the entire organ. It is star-shaped, and radiates
connective tissue septa out into the parenchyma to support and separate
the tubules. Ellenberger states that the testis of the bull and all
ruminants lacks a closed system of interlobular septa, because of the
feeble development of the connective tissue.
The principal blood vessels and rete tubules are found in this
structure, the function of the latter being to connect the seminiferous
tubules and the efferent tubules of the epididymis. The epithelium of
the rete is quite irregular,—consisting in places of a single layer; in
others, of two layers. At some points there are formed groups of several
cells lying over one another, with swollen homogeneous basal cells,
which sometimes form projections into the lumen.
The interstitial tissue, besides conveying the blood vessels to the
organ, contains many “interstitial cells.” These cells are relatively
sparse in the adult bull, and are comparatively delicate, slightly
granular, often shuttle-shaped, with a rather small nucleus.
Embryologically they are derived from a syncitium arising from the
mesothelium of the genital ridge, differentiating out by growth of the
cytoplasm. They contain large quantities of fat, and elaborate the
internal secretion of the testis. This secretion governs the development
of the secondary sexual characters, and has a profound influence on the
general body metabolism, and development of the skeleton. The
interstitial cells appear early in embryonic life even before there is
any differentiation of sex, and their greater relative development in
the fetus is indicative of a future male development. In very young
embryos, the growth is very rapid, followed, however, by a period of
atrophy, during which the seminiferous tubules undergo marked
development. Pende (21) states: “There seems to be an inverse relation
between the growth of the tubular and interstitial tissues, as one is
hypoplastic when the other is in full activity.” From birth to the onset
of sexual maturity, which may be called a period of rest for the
testicle, the cells are few in number. With the accentuation of the
secondary sexual characters, and the beginning of sexual life, these
cells again increase in number and activity.
The parenchyma of the testis consists for the most part of the
seminiferous tubules, which, on account of the courses they take in the
different regions, are divided into groups. The peripheral tubules are
the much-contorted tubuli contorti. These anastomose to form the much
shorter tubuli recti. These in turn anastomose frequently, uniting to
form the rete testis. The rete proceeds through the mediastinum to form
the efferent ductules which break through the tunica albuginea to form
the greater part of the head of the epididymis. The tubuli contorti are
the longer and more numerous of the tubules, for it is here that
practically all the spermatozoa are produced. The straight tubules are
relatively so short that they may be regarded more in the light of the
beginning of the system of excretory ducts.
The seminiferous tubules consist of a thin peripheral membrana propria
upon which rests the seminal epithelium, which is made up of the
essential semen forming cells, and the cells of Sertoli. The
spermatogenic cells may be divided into three groups, from within
outward: the peripheral single layer of small cuboidal spermatogonia;
one or two rows of large spermatocytes; and three to five rows of
spheroidal spermatids. The cells of Sertoli are more or less of the
syncitial type,—large in size and irregular in outline. They occur at
various intervals between the layers of spermatogenic cells, with their
bases resting upon the membrana propria. Centrally they send out
protoplasmic processes for variable distances,—some even reaching the
border of the innermost cell layers.
SPERMATOGENESIS: In this process, the primary germinal cells, the
spermatogonia, divide to form the primary spermatocytes. Maturation
consists of two cell divisions of the primary spermatocytes, and these
in turn form four spermatids. During the process, the number of
chromosomes is reduced to half the number characteristic of the species.
The spermatids then become converted into mature spermatozoa. This mode
of transformation may be seen in Plate I. In the process, the nucleus of
the spermatid forms a large part of the head: the centrosome divides,
part passing to the extremities of the neck. One centrosome becomes the
anterior, and remains attached to the head, while the other divides to
form the posterior centrosome. The latter is divided into the anterior
part, and the posterior nodule or annular ring. Besides this, the
posterior centrosome becomes elongated to form the axial filament, and
the cytoplasm forms the sheaths of the neck and tail. The spiral
filament of the connecting piece is derived from the cytoplasmic
mitochondria. At this time, a large part of the cellular cytoplasm is
cast off. Meanwhile, the spermatozoa sink their heads into the long
protoplasmic processes of the Sertoli or “nurse” cells which furnish
nutritive material for their complete development. Finally the adult
cells are cast off into the lumen. The structure of the spermatozoa, and
a discussion of the semen will be taken up later.
EPIDIDYMIS: The epididymis is divided into three parts: the head, body
and tail. The head is made up principally of the lobules formed by the
much-coiled efferent ductules proceeding from the rete. The ductules,
about twelve in number in the bull, unite to form the body, which
remains coiled and runs along the postero-medial part of the testicle to
which it is more or less closely attached. To quote Ellenberger (23):
“The transition from the rete into the ductules is gradual, as the
characteristic epithelium of the latter (ductules) begins in cavities
without walls, and at first, gradually form a wall which is well marked
out as a thin ring of interstitial tissue.... The epithelium of the
ductules is in sharp contrast to the rete in that it has a
single-layered ciliated columnar epithelium, in which here and there one
finds round basal cells. The dark and light columnar cells alternate;
the cilia are often cemented together, and form cone-shaped, homogeneous
appearing protuberances. The secretory activity is quite clearly
observable. In the light cells one finds secretory globules,
accumulating in rows, sometimes above, other times below, arches of
cells. The secretory droplets pass from the cells into the lumen, and
often lie in irregular layers on the epithelium; also the basal cells
appear swollen and shoved out between the cylindrical cells.” At the
lower extremity of the testicle, the tail is formed, which is globular
in shape, and more or less loosely attached to the testicle. Here the
ductules anastomose freely, gradually become less coiled, and end in the
single excretory tube, the vas deferens. The epithelium at the tail part
is more or less of the pseudo-stratified columnar, ciliated variety.
Outside this is a membrana propria, a circular muscular layer, and a
connective tissue coat. The secretory activity is very marked here and
one finds much secretion in the lumen, Courrier (24), working on the
bat, suggests that the glandular activity is conditioned by the
secretion from the interstitial (endocrine) gland. The action of the
secretion is to dilute the large mass of spermatozoa present, nourish
them to some extent and also stimulate them to active motility. Stigler
(25) states that the properties of the sperms are modified in the
epididymis; the motility, the ability to resist heat, and other
properties are augmented, at least in the case of the guinea pig, rat,
and mouse. Some authors state that the sperms first become motile when
in contact with the prostatic secretion, but I have repeatedly examined
the contents of the tail of the epididymis of the bull, rabbit, and
guinea pig, finding full motility in each case, though the duration is
not nearly as long as when the sperms are ejaculated in the semen.
The VAS DEFERENS is quite narrow (2 mm.) and runs from the tail of the
epididymis to the verumontanum, or colliculus seminalis, where it
empties into the urethra in common with the duct of the vesicle. At
first it is lined by epithelium similar to that of the vas epididymis,
but this changes over into a peculiar low stratified type. Ellenberger
describes it as follows: “The epithelium shows a very pronounced basal
coat. The overlying cell zone shows more (at the most, three) rows lying
over each other of elongated nuclei, while an outline of cell form is
not ordinarily noticeable, so that it may be spoken of as a syncitium,
and at the same time as a many layered epithelium.” The mucosa forms
low, broad folds into the lumen. The tunica propria is a thin connective
tissue layer. The submucosa consists of thin connective tissue. Three
muscular coats are present: an inner thin longitudinal layer, middle
circular layer, and an outer longitudinal layer. All are more or less
intimately blended, and are surrounded by the adventitia, made up of
connective tissue, elastic fibres and scattered longitudinal muscle
cells of the internal cremaster muscle. Near the dorsal surface of the
bladder, the ducts come in close apposition, and for ten to twelve
centimeters dilate to form the ampullae. Here the mucous membrane
becomes much plicated, forming long folds which anastomose freely. The
function of the vas is to convey the spermatozoa and secretions from the
epididymis to the urethra. Disselhorst (26) believes the ampulla acts as
a seminal reservoir and states that he has found spermatozoa stored up
in the little pockets in the walls of this structure in animals during
the rutting time. He suggests, further, that there is a relation between
the state of development of the ampulla and the time occupied by
copulation. When the organ is small or absent, as in dogs, cats, and
boars, the coition is a slow process, but when the ampulla is large and
well developed, as in horses and sheep, the coitus requires a relatively
short time. Inasmuch as coitus is so rapid in the bull, and the ampulla
is so well developed, it seems as though this function is very probable.
The SEMINAL VESICLES are very compact glandular structures lying on
either side of the median line, on the dorsal side of the bladder, and
ventral to the rectum. In the mature bull they measure ten to twelve
centimeters in length, four centimeters in width, and about two and
one-half to three centimeters in thickness. The glands are distinctly
lobulated, quite tortuous, and are often asymmetrical in size and shape.
They converge posteriorly, to empty into the urethra at the colliculus
seminalis with the ampulla, in a slightly oval slit in the mucosa.
Microscopically, the gland is of the anastomosing tubular type, with
very poorly developed excretory ducts to the glandular cavities.
Posteriorly one finds centrally a few sinus-like narrow excretory
passages, which open into the somewhat larger collecting and excretory
duct. The epithelium is of the simple columnar type and produces a
relatively large amount of secretion. The gland cavities are surrounded
by a membrana propria, over which is a relatively thick layer of smooth
muscle. Outside this is a connective tissue covering which sends
trabeculae or septa in between the lobules. The secretion of the seminal
vesicles is a tenacious albuminous fluid with a slightly yellowish
tinge, all or part of which appears in the ejaculate in the form of
swollen sago-like grains which are soon dissolved following ejaculation
and the liquefaction of the semen. The proteid compounds belong to the
group of histones. The secretion is liquid when warm and coagulates when
cold. Some say that the filling of the vesicles serves to excite sexual
feeling, but this is doubtful in view of the fact that in some animals
the sexual desire exists before the vesicles are filled. Likewise,
Steinach found that rats, whose seminal vesicles had been removed, still
retained their desire for copulation. The function of the secretion is
to furnish much of the volume to the semen, and in some way it has a
distinct bearing on fertility, inasmuch as extirpation of the organs in
rats leads to lowered fertility. The vesicles of the bull are in no
sense a store-house for spermatozoa, as is usually understood. Repeated
examinations in a large number of bulls have led to the finding of
spermatozoa there only in very rare instances. That they serve as a
resorption place for sperms that are not ejaculated is also very
unlikely. Normally, one sees on smear of the vesicles, occasional cells,
leucocytes, lecithin granules, sago bodies, and rarely a few degenerated
spermatozoa.
The COLLICULUS SEMINALIS is a rounded or cone-shaped eminence in the
posterior urethra, upon which the ducts of the seminal vesicles and vasa
deferentia open. The ducts open separately at the bottom of two narrow
slits, one on each side of the mound, there being no distinct
ejaculatory duct as in man. The function of the colliculus or
verumontanum is not definitely known. It is generally believed that the
structure is made up of blood spaces which become engorged during
erection, causing a blockage of the posterior urethra, which prevents
regurgitation of the semen. Rytina (27), however, demonstrated that the
structure is not composed of any unusual number of blood vessels or
spaces, and that removal of the organ was not followed by regurgitation
of the semen into the bladder during ejaculation. He believes, and quite
logically, that its function is to afford a prominence upon which the
ducts may empty. The mixture of the thick gelatinous semen with the thin
prostatic secretion must occur at the moment of ejaculation and must be
perfectly homogeneous, otherwise large numbers of the organisms remain
in the thick gelatinous portion of the fluid. The eminence serves this
purpose in that the prostatic ducts which converge toward it, may eject
their secretion toward the eminence, producing an admixture more evenly
and quickly.
PROSTATE: The bull possesses what Ellenberger calls a diffuse prostate.
That is, there is no distinct glandular body as in man. It is composed
principally of a glandular sheath around the urethral wall. Just
posterior to the neck of the bladder, and in front of the urethral
muscle, there is formed a slight dorsal transverse elevation, extending
downward on the sides. This is what might be termed the body. The
greater part of the gland is “disseminate” in form, being a sheath of
glandular tissue embedded in the urethral wall. Dorsally it is about ten
to twelve millimeters thick, and ventrally about two millimeters. The
gland is a branched tubular structure, the interlobular tissue of which
contains much unstriped muscle. The lobules are lined by a columnar type
of epithelium. The ducts, about thirty to forty in number, open into the
urethra in two rows posterior to the colliculus. The secretion is a
thin, slightly turbid fluid, of a faintly alkaline reaction. Its
function is to dilute the semen, stimulate the motility of the
spermatozoa and nourish them.
Fish (28) believes that the activating property of the secretion is due
to enzymes, because boiling deprives the fluid of its power to
accelerate the motility of the spermatozoa. Serrlach and Pares, quoted
by Marshall (29), working on dogs, have adduced evidence indicating that
the prostate is an internal secretory gland which controls the
testicular functions, and regulates the process of ejaculation. It is
stated that if the prostate is removed, spermatozoa are no longer
produced in the testis, and that the secretory activity of the accessory
genital glands ceases. These changes, however, can be prevented by the
administration of extracts of the prostate. The fact that the prostate
elaborates a secretion having a definite relation to the testis, has
been verified by other authors.
COWPER’S GLANDS (Bulbo-Urethral): These glands are paired, oval
structures about one and one-half by two and one-half centimeters in
size, situated on either side of the dorsal pelvic part of the urethra
close to the ischial arch. They are deeply embedded, with the bulbus
urethae, in the bulbo-cavernosus muscle, thereby being inaccessible to
palpation. In general, they are of a well developed anastomosing tubular
type. The connective tissue stroma is relatively thin, and thickens only
in between the larger lobules, where one finds the larger collecting
ducts. Each gland opens by a single duct. The epithelium is of the
simple cuboidal type. Little is known of the function of its secretion,
though Kingsbury (30) regards it in the light of a mating gland; that
is, it lubricates the genital passages during coitus, as does its
homologous structure in the female, Bartholin’s gland.
Ellenberger describes the urethra, slit ventrally, as presenting the
following picture: “The colliculus seminalis distinctly appears as a
process or offshoot of the crista urethralis of the Trigonium Vesicae.
At the summit, and at the bottom of the two slits, open laterally the
ducts of the vesicles, and medially the ductus deferens.... From the
caudal slope of the colliculus go two distinct mucous membrane folds
which run through the entire pelvic urethra, near together, somewhat
diverging, and then coming together, so that they form an elongated,
narrow oval. At their caudal union, the excretory ducts of the
bulbo-urethral glands open side by side. At the point of departure of
the folds from the colliculus, arises a niche-shaped opening, between
both folds, and likewise lateral to each fold. In these niches open the
ducts of the prostate. The openings of the disseminate prostate lie in
rows as in the horse, but form not less than six rows. There is one row
medial to each fold, and two lateral. Mullet mentions only the medial
rows. These rows extend to the opening of the ducts of Cowper’s glands.
The stratum glandulare (disseminate prostate) is very easy to recognize
with the naked eye.”
SEMEN: The semen is the mixed product of the testicles, their excretory
passages, and the accessory sexual glands, a fact which complicates its
study considerably. The freshly ejaculated fluid is cloudy, tenacious,
more or less coagulable, and is rich in albumen. It is weakly alkaline
in reaction, and contains eighty to ninety per cent of water. Of the
solid constituents, there is forty per cent of ash, of which
three-fourths is calcium phosphate. Besides the spermatozoa, the semen
frequently contains epithelial cells, leucocytes, concentric amyloid
concretions, and lecithin bodies. When cold, the characteristic
phosphoric acid salts are precipitated. The fluid content is the product
of the tubules of the testicles, their excretory ducts, and the
accessory sexual glands. The characteristic odor of the semen is
supplied by a slimy nucleoalbumen “spermin” which forms the spermatic
crystals, and is furnished by the prostatic secretion.
During ejaculation the spermatozoa and secretions added by the testicle
and epididymis are probably carried to the ampulla by peristaltic
muscular action, in the earlier stages of the orgasm. At the height of
the orgasm, the ampulla is emptied into the posterior urethra in common
with the secretion of the contracting vesicles, here to be admixed with
the thin prostatic secretion. The entire mixture is then propelled, and
ejaculation produced by strong muscular contractions of the entire
urethra. As was stated before, the semen is the product of the
testicles, the excretory ducts, and the accessory sexual glands. The
testes furnish the essential germinal elements, the sperms, and some of
the fluid content. Then is added the product of the epididymis, vas, and
ampulla, which stimulates the spermatozoa to active motility, nourishes
the organisms, and adds somewhat to the fluid bulk of the secretion.
Stigler (25) states: “During its sojourn in the epididymis, the
properties of the spermatozoa are modified; the motility, ability to
resist heat, and other properties are augmented, at least in the case of
the guinea pig, rat, and mouse.” To the secretion is then added the
product of the vesicles, which contributes markedly to its fluid
content, nourishes the sperms, and supplies the ferment which induces
clotting of the semen when ejaculated. This is very important because
the clot formed in the vagina protects the delicate spermatozoa from the
hostile acid vaginal secretion. The prostate likewise adds bulk and
nourishing substances, besides stimulating the spermatozoa to fuller and
more lasting motility. The addition of the spermin is perhaps
unimportant. The function of the secretion of the Cowper’s glands, which
is added at this time, is problematical. It does, however, have a
diluting action on the semen. Perhaps its secretion is poured out prior
to ejaculation so as to lubricate the canal and prepare the way for the
semen.
Fish (28) has demonstrated by means of darkfield illumination, the
presence of numerous minute particles or ultraparticles in this fluid.
Their character and significance are matters of conjecture, but it would
seem as though they were not identical with the “chylomicrons” or fat
particles found in the blood by Gage. Perhaps further researches will
reveal some intimate connection between the number present in a field,
and the relative potency of the animal.
Each portion of the tract furnishes some essential element to the mixed
product which is so remarkably adapted both as a vehicle for the
ejaculation of the spermatozoa, and as a fluid in which their motility
is initiated and maintained. Any derangement of one part is fraught with
danger to the existence of viable spermatozoa, and the continuation of
full fertility on the part of the animal. The physiology of each
contributing gland must be borne in mind at all times. Walker (31)
investigated the fertility of the semen of the dog, taken from various
parts of the tract. His results were: (1) semen from the testicle and
head of the epididymis showed no motility, (2) semen from the tail of
the epididymis showed some motility in the more fluid contents of the
preparations, (3) semen from the vas deferens appeared about the same,
(4) a mixture of epididymis semen and prostatic secretion showed active
motility, and (5) likewise in a mixture of epididymis semen, though only
in those places where the fluids had become well mixed. My observations,
however, differ in one respect with regard to the bull, as I have found
full motility of the spermatozoa from the epididymis, but it is not so
lasting as when augmented by the addition of the prostatic fluid.
Boettcher (32) concludes: “that the secretion of the accessory male
genital organs possesses a protective colloid, which (1) hinders the
spermatozoid action of the vaginal secretion, at least until the sperms
have time to reach the interior of the uterus which is an alkaline
reaction, (2) that it makes the ejaculate more voluminous, so that by
cohabitation, a very good part of the vagina becomes moistened, and the
spermatozoa become distributed over the greater part of the vaginal
mucosa. This distribution is rendered necessary because some of the
fluid flows from the vagina following coitus. In this manner the
opportunity is given for a part of the ejaculate containing the
spermatozoa to be brought easier to the external os, and (3) it happens
that because of its content of sodium chloride the life of the
spermatozoa is stimulated and prolonged.” A fuller discussion of the
essential physiology of the various parts of the tract on the semen
content, and fertility, will be taken up later. The changes in
biochemical content, reaction, and the result of the addition of
bacterial products will also be more fully discussed.
SPERMATOZOA: The history of the discovery of spermatozoa is very
interesting, and for that reason a brief outline will be given. The
“semen threads” were first observed in the year 1667, by Ham, a student
of Leeuwenhoek at Leyden. The discovery was announced, confirmed by
findings in the dog and rabbit, and discussed by the latter author under
the title: Observationes Anthonii L. de natis e semine genitali
animaculis (Upon the formation of young from procreative material). The
sperms were taken to be animals on account of their motility, and their
significance remained questionable if not unknown. Spallanzani, quoted
by Marshall (29), was the first to show that the filtered fluid was
impotent, and that spermatozoa in the semen were essential to
fertilization. Kolliker, in 1841, discovered that the sperms arise from
the cells of the testis, and Barry in 1843, observed the conjugation of
sperm and ovum in the rabbit. This led to a clear understanding of the
function of these important germinal elements.
The spermatozoa are the male procreative cells, and are characterized by
the possession of a head containing the chromosomes necessary for
fertilization, and a tail capable of propelling the organism on its way
to meet the ovum. The length of the entire sperm, including the head, is
seventy-five to eighty microns. The head is nine and five-tenths microns
long, and five and five-tenths microns wide. It may be divided into two
principal parts, the head and tail. The head, for the larger part, is
made up of the nucleus, and may be differentiated by staining reactions
into a darker staining posterior part, an anterior lighter part, and
often a still lighter area between the two. On the anterior part is a
sharpened edge, the acrosome, which serves to perforate the ovum. The
whole is surrounded by a very definite limiting membrane which often
becomes obscured under abnormal conditions. The tail may be divided into
three parts: connecting piece, principal part, and terminal filament.
The connecting piece, the essential motile apparatus, is the thickest
and strongest part, and joins the tail proper to the head. It consists
of the central axial filament, a spiral filament around this, and an
outer mitochondrial covering. Anteriorly it is limited by the anterior
portion of the posterior chromosome, and posteriorly by the annular
chromosome. The anterior chromosome is directly connected with the head,
there appearing a light break here at the neck where separation
frequently occurs. This neck serves as a joint for the motion. The axial
filament, therefore, does not reach the head, but extends back from the
anterior part of the posterior chromosome. The principal part consists
merely of the axial filament, and a thin outer covering, while the end
piece is quite thin and is made up solely of the uncovered axial
filament. The finer structures are seen only when special staining
reactions are used, and then only when the sperms are obtained directly
from the testicle. The function of the sperms is of course primarily
that of fertilization. Numerous observers have, however, thought that
they might have some other definite, though unknown, use.
An editorial in the Journal of the American Medical Association (33)
raises several important questions regarding this obscure phenomenon.
The fact that an enormous number of spermatozoa are produced, and only
one, or at most, a few perform the function of fertilization, raises the
question as to what becomes of the remainder. It is stated: “Zoologists
have found that in some of the invertebrates the spermatozoa invade the
entire body of the female, and in some species they reach the ovum by
penetrating the cuticle from outside and migrating to their goal.
Studies on rodents show that the sperms invade the epithelium of the
generative mucosa and underlying connective tissue. These tissues seemed
to be stimulated to growth, suggesting that this may influence the
uterine mucosa in its preparation for receiving and embedding the egg,
and in forming the decidua.” It has been shown that the sperms contain a
specific protein capable of producing antibodies in the blood plasma, by
citing the fact that rabbits develop a distinct Aberhalden reaction for
testicular proteins shortly after cohabitation. One very important
observation showed that by immunizing female rabbits with sperms they
were rendered sterile for some time, although after a few months they
again became capable of impregnation. The question raised is: “... if
the spermatozoa invade the female tissues and cause the formation of
specific antibodies which are capable of preventing fertilization, may
not such a process participate in the problem of sterility?” This very
problem seems to be a factor in explaining why some couples who are not
fertile to each other subsequently are both fertile when they cohabit
with other individuals.
_Motility_: After clinical observation of the motility of the
spermatozoa of the bull, I find that it differs little or none from the
types as observed by Reynolds (34) in his work on human spermatozoa. His
observations are so accurate and well described that they will be given
in his words. “All normal motions appear to be consecutive phases.
Initial motion, i. e., motion as seen in fresh semen under favorable
conditions, consists of a lashing of the after part of the tail from
side to side which is so rapid as to constitute vibration. It produces
rapid forward motion in a practically straight line, the head, middle
piece, and forward portion of the tail maintaining their position in the
line of motion with practically no swaying from side to side. The action
of the flagellum is so rapid that it is quite impossible to follow its
individual movements. Spermatozoa swimming in this manner head against
the current and usually cross the field of observation in about five
seconds in the absence of currents or obstacles. This type of motion
will be described throughout the paper as ‘progressive vibratile’
motion. Progressive vibratile motion is normally succeeded after a
variable length of time by what I regard as the second phase of normal
motion.
“The second normal motion differs from the first not only in its
character but in markedly reduced speed. The tail movement alters to a
long stroke from side to side and almost the whole length of the tail
partakes in the stroke. This is, moreover, accompanied by swaying of the
head and middle piece through an arc which is always considerable and
may even equal ninety degrees. The general outline of the spermatozoa,
from being practically straight with almost non-detectable sharp, quick,
small arc vibration of the after-tail, has become an S in outline, with
large, slow, plainly perceptible undulations traveling gradually
backward throughout the length of the spermatozoon. Speed has been lost
and direction seems to be more specifically determined by the
surroundings. Individuals at this stage show a pronounced choice of
direction and go up to objects in the medium, from which they later make
off as though the movement were determined by tactile reaction to some
extent. This type of motion has, therefore, been named ‘undulatory
tactile’ in contradistinction to ‘progressive vibratile.’
“The third type of normal motion succeeds the second and consists in a
tendency on the part of the spermatozoon to push itself against or into
any small masses of cells, or sometimes other materials, which it may
find in the neighborhood, bunting itself into any small cove that can be
found, and maintaining a slight burrowing motion by a lashing tail
movement of the vibratile type not unlike the movements of the caudal
fin of a fish. The movement of the flagellum in this third type is
unlike the second type in that it is vibratile rather than lashing, but
is slower than the vibratile motion of the first type and less limited
to the afterpart of the tail. These spermatozoa are apparently not
caught in the debris or unable to move off. From time to time, they back
out of such a cove and seek another mooring place.
“This ‘stationary hunting’ motion is less universal than the other two.
Many individual spermatozoa fail to attain it. It seems probable that
only the most vigorous individuals ever reach this stair”. It has not
been encountered in unmixed semen or in any artificial mediums. It has
been observed only when the spermatozoon is in the secretions of the
female genital tract. It is most frequent when the spermatozoon is in
contact with a nest of epithelial cells....
“The three types of normal motion are not only distinctive but are
always consecutive, i. e., the second follows the first after a period
which is apparently determined both by initial vitality and by the
favorable or unfavorable character of the medium, while the third has
been observed to occur only in individuals which have already developed
the second. They apparently constitute a normal cycle.
“This cycle is open to the theoretical explanation that these types of
motion are directly adapted to the function of the spermatozoon; thus,
the progressive vibratile motion which is characteristic of the earliest
period of its existence appears especially suitable for its prolonged
journey through the cervix and uterus to the fundus and tube. This is
supported by the fact that during this motion it always heads directly
against any existing current, and that during this stage of its journey
it must under natural conditions be continuously exposed to the faint
outward ciliary currents of the mucous membrane of these passages.
“The undulatory tactile motion which succeeds the progressive vibratile
would then be well adapted to the later stage in which the spermatozoon
has reached the tube, where its success in conjugation is dependent on
its finding the ovum rather than on further progress.
“The stationary bunting type of motion is that which would be demanded
by the passage of the spermatozoon through the egg membrane which has
been so often observed in the lower animals. This very plausible
explanation is, however, necessarily theoretical and must always remain
so, as the conditions which surround the specimen on the field of the
microscope vary in so many respects from those in which it accomplishes
conjugation in the course of nature; but the practical importance of the
study of types of motion is not affected by their explanation.”
The duration of motility is a variable factor, dependent entirely upon
the environment in which the spermatozoa are placed. Within the body
they usually survive at least a week. One author describes a case in
which he found living sperms in a woman who stated that coition had not
been experienced for three and one-half weeks. It has been stated with
regard to human sperms, that their motion should continue or be capable
of being re-established for twelve hours. Cary (35) states, “first, that
in their proper medium and at the body temperature the viability of the
sperm cells may extend over a period of a few days; second, that their
prolonged vitality is probably dependent upon the normal lime salts of
the prostatic fluid; third, that the sustaining power of the seminal
fluid is increased by its union with the normal secretion of the female
genital tract.” After death of the male animal they retain their
motility in the genital tract for twenty-four to forty-eight hours.
Wolf (36) worked on this problem in rabbits, and summarizes as follows:
“The motility of rabbit spermatozoa can be preserved for at least nine
days by placing the juice of the epididymis in the Tyrode solution which
had been buffered and to which glucose had been added. The solution is
adjusted to a pH of about 7.4. Oxygen is passed in and a suitable amount
of sodium bicarbonate added. The preparation must be kept at a
temperature near the freezing point of water.” Under ordinary conditions
motility persists outside the body only a few hours after ejaculation,
but if the semen is kept quite cool till the time of examination on a
warm stage, motility should be capable of being restored in at least a
fair percentage of the sperms for twenty-four to forty-eight hours. The
cells are more sensitive to heat than to cold, and even to dilute acids
more than to alkalies.
Henle (quoted by Ellenberger) states that a spermatozoon under favorable
conditions travels at the rate of twenty-seven millimeters in seven and
one-half minutes, which makes three and five-tenths millimeters per
minute. This is about sixty times the entire length of the spermatozoon,
and twenty-one centimeters in an hour. Forward motion is also more
pronounced when the swim is against the current, such as is produced by
the cilia of the oviduct. It has been demonstrated that feebly motile
sperms become very actively motile when placed on the mucosa of a fresh
Fallopian tube.