Definition. Transitory only. Causes, kidney disease, drinking freely,
rich feeding, profuse secretion, polycythemia, hyperalbuminosa, excess
of fibrine, sugar or fat. Ratio of blood to body. Variations of
globules. Symptoms, general, local. Appearance of blood. Prevention.
Treatment.
_Definition._ An excess of blood, of the blood globules, or of the
albuminoids.
Formerly accorded an important place in pathology, plethora has been
entirely eliminated from some recent works. The actual amount of blood
varies greatly at different times, rising after a free consumption of
food or drink, and falling during a period of abstinence. A healthy
activity of the secretory and excretory organs secures a fair uniform
average in the plenitude of the circulatory system. Moreover, large
variations are not in themselves rapidly injurious. Worm-Müller and
Cohnheim introduced into dogs ten to twelve per cent. of the body weight
(fifty to eighty per cent. of their blood) of canine blood without
inducing fatal results. More than this was fatal. In non-fatal cases a
reduction to the normal standard is speedily secured.
But we cannot count on absolute immunity in all circumstances. Disease
of the kidneys, or drinking water to excess, determines a surplus of
water and urinary salts (serous plethora, polyæmia aquosa). In cases of
rapid gain in condition from rich feeding, and above all after profuse
watery secretion (diarrhœa, diuresis, perspiration), the red globules
are relatively increased (plethora polycythæmica). After hearty feeding
there is a large increase of albumins (plethora hyperalbuminosa).
Fibrine-forming elements are apparently in excess during rheumatism,
pneumonia and other acute inflammations. Sugar is in excess after a
saccharine or farinaceous meal, fat in obese individuals, after
consumption of fat, after injuries to the bone marrow, and after severe
diseases with much destruction of albumen.
The ratio of blood to the body weight is: In birds 1: 12; in Guinea pig
1: 19; in rabbit 1: 20; in cat 1: 21; in dog 1: 17; in horse 1: 18; in
sheep 1: 24; in pig 1: 26; in ox 1: 29 (Colin). As showing the variation
under even different normal conditions of the system Bollinger found the
blood but 2.2 per cent. of the body weight in a fat pig, whilst it was
13.5 per cent. in a draft horse. Colin found it 2.4 per cent. in the fat
ox instead of the usual 3.4 per cent.
The excess of red globules and usually also of albumins is seen as a
temporary condition, in lean but vigorous animals put suddenly on an
abundant diet, rich in assimilable albuminoids, in working animals, put
in confinement to feed, and above all in high conditioned cows after an
easy parturition, when the uterine blood has been suddenly thrown on the
general circulation and the emunctories have failed to establish a
balance. Also in the lymphangitis occurring after a day or two of rest,
in a horse that has been hard worked and heavily fed.
It should be borne in mind that the number of red globules varies
considerably in the different animals. In the dog it was by weight 148.3
grammes per 1000; in the pig 105.7; in the horse 102.9; in the ox 99.71,
and in the sheep 98.2 (Andral, Gavarret, Delafond). By count the horse
has 5,500,000 per cubic millimeter (7,500,000, Nocard); and the dog
5,000,000.
_Symptoms._ Under a sudden dangerous increase of the volume or the
organic elements of the blood, there are usually dulness, lassitude,
dropping of the head, strong, full, hard pulse, extra force in the heart
beats, thirst, elevated temperature, and redness of the visible mucous
membranes. At first there is no indication of local disease, but unless
relief comes by free secretion some local complication is likely to
ensue. This may be epistaxis, congestion or apoplexy of the brain,
parturition fever, lymphangitis, or congestion of some internal organ,
etc. A drop of blood colors deeply the finger or other object, it clots
firmly in three to five minutes, and shows more than usual of a buffy
coat.
_Treatment._ As dangerous plethora is usually a very transient condition
the main attention should be given to _prevention_, in keeping the diet
low and the emunctories active in high conditioned parturient cows; in
lowering the diet and securing free secretion, or in giving exercise to
high fed, hard worked horses that have been laid off work; in changing
only by slow gradations thin, vigorous animals to a rich diet, etc. When
the danger is imminent prompt relief can be secured by the liberal
abstraction of blood. Purgatives, diuretics, and restricted diet may be
applied to less urgent cases.