A system of practical medicine. By American authors. Vol. 1

by Unknown

Another theory is, that cow-pox is really small-pox modified, as the phrase runs, "by passing through the system of the cow." It has been thought possible, indeed, to specify in what way the cow's system could impress such decided changes upon the virulent disease small-pox as to convert it into the mild affection that we know as vaccinia; in other words, it has been imagined that the function of lactation accomplished this remarkable result. This notion may have been due to the observation that so-called spontaneous cow-pox is met with only in cows that are in milk. The significance of this fact, however, is really nothing more than that cows in milk are more exposed to accidental inoculation than other bovine animals—namely, at the hands of the milkers. The fact that in such cases the lesions are almost always confined to the teats and the udder, far from affording any ground for the notion that there is some mysterious connection between cow-pox and the function of lactation, is but another proof that the disease is the result of inoculation. The lesions appear at the points of inoculation, the teats and the udder being the parts handled by the milkers. Moreover, there is no difficulty in inoculating young calves or adult bulls, and the lesions so produced do not vary in a single particular from those observed in so-called spontaneous cases.

Men have been so carried away with this milk theory, however, as even to believe that the virus of small-pox might be shorn of its dangerous properties, so that it would produce only the vaccinal lesion when inoculated simply by mechanical mixture with milk. During the late Civil War one of the Confederate Army surgeons actually put this notion to the test of practice on quite a large scale, inoculating large numbers of persons with a mixture of small-pox virus and milk, terming the practice mitigated inoculation. We can scarcely suppose that he did anything else than variolate these persons, just as he would have done had he used variolous lymph without the addition of milk. His experiments show nothing new; they merely furnish a recent confirmation of the well-known fact, familiar to the old inoculators, that inoculated small-pox is sometimes exceedingly mild in a series of cases.

This theory of the variolous origin of cow-pox, and of the practicability of converting small-pox into cow-pox at will by "passing it through the system of the cow," has taken deep root in the minds of men, especially in Great Britain, where the late Mr. Ceely's experiments and Mr. Badcock's experience seemed to give it some color. Some years ago, however, the question was investigated most practically and thoroughly by a commission appointed for the purpose by one of the medical societies of Lyons, Chauveau being the recorder. Their conclusion was—and their reasoning seems to the present writer incontrovertible—that small-pox and cow-pox were wholly distinct from each other under all circumstances, and that it was impossible to convert the one into the other. But the doctrines of the English investigators, reinforced as they were by the ingenious arguments of the late Dr. Seaton, were not easily to be overturned in their own country or in America; consequently, the practice of variolating cows has been resorted to from time to time for the purpose of obtaining a stock of vaccinal virus of unquestionable authenticity—the so-called variola vaccine. This practice is utterly fallacious, and it is also dangerous, since the disease so produced, however mild it may seem to be, is nothing more nor less than small-pox, with its infectiousness by effluvium and its liability to prove serious even when carefully inoculated.

Quite recently the experimental investigation of the question has been undertaken de novo by a well-known English veterinarian, Mr. Fleming; and, since his conclusions coincide with those of the Lyonnese commission, it is to be hoped that we have seen the last of this rough-and-ready method of improvising a case of genuine cow-pox—a method that, in the light of our present knowledge, can only be characterized as downright malpractice.

The third and last theory we have to consider is that which ascribes the origin of cow-pox to infection from the horse. So far back as Jenner's time it was conjectured that cow-pox was due to the accidental conveyance of the virus of the grease (the eaux-aux-jambes of the French) by reason of the cows being milked by persons who were also employed in the care of horses affected with that disease. Grease is an eruptive disease of horses' heels. Doubtless it has often been confounded with a mere eczematous affection by those who have repeatedly failed in their persistent attempts to inoculate cows with it, and, on the other hand, a localized eruption of horse-pox may have been mistaken for it by those who have supposed themselves to have succeeded in producing cow-pox by inoculating cows with the virus of grease, and have consequently given in their adhesion to the grease theory of the origin of cow-pox. At all events, so far as the writer is aware, that theory is not now held by any well-informed writer.

Still regarding the horse as the originator of cow-pox, we must turn our attention to horse-pox (equinia). Several years ago Depaul of Paris took great pains to establish the fact that horse-pox (an affection totally distinct from grease) was an eruptive febrile disease of horses, an exanthem; that the eruption was generalized, and, being for the most part concealed by the hair, generally overlooked; and that it was capable of being conveyed by inoculation, the lesion being indistinguishable from that of cow-pox. He believed himself to have demonstrated also that it was the contagion of horse-pox that gave rise to cow-pox in the cow.

Depaul's investigations were very keen and his conclusions were exceedingly plausible, but they cannot be called convincing, notwithstanding the fact that Constantin Paul succeeded for a time in popularizing a stock of horse-pox virus as material for vaccination. At about the same time the Beaugency case of cow-pox was discovered, and the perfectly satisfactory use that has been made of that stock may have thrown Depaul's theories and Paul's practice undeservedly into the background.

We can only say, in summing up, that the small-pox theory is utterly untenable, that the horse-pox theory has not been disproved, and that the theory that regards cow-pox as derived neither from small-pox nor from horse-pox, but as a disease sui generis, although not proved, is the most rational of all, and the most in keeping with known facts.

ETIOLOGY.—Nearly everything that could be said under this head has already been considered. It may be added that meteorological conditions have been supposed to favor the prevalence of the disease among cows. More precise observations are needed to enable us to determine whether or not there is any truth in this supposition. It has been said that the affection is most apt to prevail during warm and moist seasons. This is contrary to what we might have imagined, as warmth and moisture are quite destructive of the vaccinal virus. Under ordinary circumstances, however, the contagium often proves wonderfully tenacious of life, and the disease, once introduced among a herd of cows, is prone to linger for months, or even years, attacking animals recently added to the stock and young cows during their first lactation. As has already been stated, age, sex, and parturition can be regarded as etiological factors only in so far as they favor the occurrence of accidental inoculation. In the human subject vaccinia occurs generally as the result of intentional inoculation, as will be more fully referred to when we come to the consideration of vaccination. Insusceptibility is occasionally met with, both in the cow and in man, but it is very rare. Perhaps it may be explained in some instances by the subject having really had the disease, or indeed small-pox, either before or after birth, in so mild a form as not to have left the characteristic marks. Certain it is that the lesion does not always leave a permanent scar, especially in the cow.

GENERAL COURSE OF THE DISEASE.—This is best studied in cases that have followed intentional inoculation, for here we know the chronological sequence of events. Depending somewhat upon the method of inoculation, and perhaps also to some extent upon the state of the skin at the site of the inoculation, or even upon a systemic condition (since some vaccinators hail it as a harbinger of success), at the time of the operation a ring-like erythema may be seen surrounding the inoculation. This is exceedingly evanescent, being doubtless due to vaso-motor action, and is not often witnessed.