Text book of veterinary medicine, Volume 3 (of 5)

by James Law

Cardiac Hypertrophy. Cagny draws attention to the fact that in man and beast alike the heart undergoes hypertrophy during gestation and, above all, during its later stages. In improved breeds of cattle, and especially in milking breeds, a great development of the whole circulatory system is seen, and a large heart is a constant feature of this. This implies an increased force of cardiac systole, an increased blood tension in the arteries and capillaries, a condition which tells with special force on the soft tissues of the brain, as the violent abdominal compression in the expulsive efforts of parturition, tends to drive the blood from the great vascular viscera situated back of the diaphragm.

Parturition and the subsequent contraction of the womb and expulsion of the great mass of blood, must be accorded a prominent place among causative factors. The disease is almost restricted to the first week after parturition, and its gravity is greater the more it is related to the parturient act. Cases occurring in the first three days are usually fatal. The gravid uterus contains a very large amount of circulating blood, and when the womb contracts, the greater part of this is suddenly thrown upon the general circulation, already plethoric to an undue extent. As yet the mammæ are congested and there is no free depletion through that channel, so that there is a marked temporary plethora and vascular tension, before the system can establish free elimination and, as it were, strike a healthy balance. In this period of transient plethora there lies a source of great danger to the general system and, more particularly, to the brain.

Emotional Excitement connected with the removal of the calf is urged by Günther, Jaumain, Félizet and others as a prominent cause. This, however, must be rare, at the most; the disease does not attack the primipara that should be most susceptible to this influence, but the mature animal, at her third calving or later when she is already well accustomed to this treatment; it supervenes so quickly on parturition in many cases, that there was no opportunity for such emotion; it occurs also in cows, the calves of which have remained with them or have received no attention from them.

Absorption of Toxic Matters. The theory of a poisoning of the nerve centres is indicated in the familiar name of milk fever, suggesting an absorption, or poisonous condition of the milk. Lafosse charged the trouble on the uterine milk secreted in the cotyledons and reabsorbed in quantity. Abadie and Kaiser attributed it to the products of gastro-intestinal ferments, which acted on the nerve centres like a deadly organic alkaloid. Hartenstein incriminated the products of muscular contraction in the womb and systemic muscles during parturition. Ehrhardt invoked a similar auto-intoxication, going on before parturition and only reaching its climax in connection with that act.

Allemani and Gratia attribute the disease to the absorption of the first milk (colostrum), and there are several considerations that strongly favor this hypothesis. The disease sets in always in connection with the parturient development and congestion of the udder and the secretion of the first milk. In exceptional cases it may even appear just before parturition. Even upon the calf the colostrum operates as an irritant and purgative. Is it wonderful that, in the parturient cow, with a high state of plethora, a highly susceptible state of the nervous system, and the various concurrent conditions already referred to above, a direct poisoning of the nerve centres should appear? It is worthy of notice that the absorption from the mammæ takes place without any metabolic change, such as occurs in the stomach and liver in the case of materials digested. It is to be presumed that the hypothetical mammary poison is delivered in the brain in its pristine condition and possessed of its full force.

The doctrine is corroborated even more strongly by the successful results of treatment by the injection of a solution of potassium iodide into the udder. The iodide solution may presumably act in one or more of several ways. It is unquestionably an antiseptic, and would tend to arrest or control microbian growth and activity, thus preventing the further formation of toxins. It has a potent deobstruent action on glandular tissue, tending not only to dry up the milk, but to hold in check the leucocytic function of producing dangerous leucomaines. There is reason to believe that with regard to some poisonous ptomaines iodine acts as a direct antidote, probably uniting with these and forming new and comparatively harmless compounds. It manifestly acts in this way in the case of cryptogamic diuresis, and in cerebral congestions arising from spoilt fodder. The iodide tends further to act as a calmative to the nerve centres, and as a diuretic, serving to eliminate the poison that may be present in the blood.

Microbian Infection or Intoxication. The doctrine has been advanced that the disease is either a microbian infection of the nerve centres or a process of poisoning by the absorbed toxins of microbes. Of the two hypothesis the latter is the more acceptable, in view of the fact, that cows in a condition of coma will sometimes recover with extraordinary rapidity. This is more likely to occur in connection with the elimination or exhaustion of a transient narcotic poison, than with a deadly microbe colonized in the brain. This hypothesis is in full accord with the acknowledged success of the iodide injections; with the observation of Bissauge, which I can endorse, that certain villages and hamlets habitually furnish cases of parturition fever, while neighboring ones, with the same breeds and apparently the same management escape; and with the observations of Russell and Wortley Axe, that the malady will sometimes be suddenly prevented in a herd, by the simple expedient of having the cows moved to a new and previously unoccupied stable, for calving and the first nine days thereafter.

In support of the doctrine of a microbian origin is recalled the fact that the disease almost invariably follows parturition, which opened the way for the introduction of bacteria by the genital passages. This is somewhat invalidated by the fact that it follows the easy parturition, in which there was no chance for the introduction of germs on hands or instruments, and does not follow dystokia in which, without question, germs have been planted abundantly in the interior of the womb. Undue weight should not be given to this objection, as the essential accessory conditions of plethora, etc., are usually largely modified in cases of dystokia.

The microbiology of the affection leaves much to be desired. Coureur and Pottiez and later Van de Velde found a streptococcus in the blood. Trinchera, Nocard, and Cozette found the common pus cocci (staphylococcus pyogenes aureus, citreus and albus) a streptococcus and a colon bacillus in the liquid squeezed from the cotyledons, and in the liquid debris on the uterine mucosa. These microbes were not found in other organs. They grew readily in artificial cultures, but we lack the final proof of a successful inoculation on a susceptible parturient subject. The whole subject is therefore still a plausible theory.

We are not however limited to the womb as the only possible field of a pathogenic microbian growth. The frequent presence of microbes in the sphincter of the teat, in the galactophorous sinus, and in the milk ducts inside the mammæ is absolutely proved. Guillebeau found on the mucosa in cases of mammitis three forms of bacillus, to which he attributed the disease. In the New York State Veterinary College we have found mammitis usually associated with a streptococcus in the milk. In one cow in the University herd which gave abundance of good milk, and rarely showed any sign of congestion, streptococcus was constantly present. In cows producing “gassy” curd, V. A. Moore and A. R. Ward found in the milk a bacillus which morphologically and in cultures resembled the colon bacillus (evidently one of the colon group). In the milk and mammary gland tissue got from other (slaughtered) cows, a micrococcus growing in yellow or buff-colored colonies predominated. (Moore and Ward). That the colon bacillus, so constant in the intestines and manure, is not always found in the milk ducts, would show that in its normal condition it is not adapted to this habitat, but when a variety appears that is so fitted, it appears to be able to maintain its place indefinitely.