VETERINARIAN.

New Zealand Mail, Issue 964, 22 August 1890, Page 20

VETERINARIAN.

DIPHTHERIA IN THE LOWER

ANIMALS. There is no novelty in the idea of the existence of some morbific matter in cow’s milk which may induce diphtheria in man. Many years ago Dr Ballard, the medieal officer for the Islington District, suggested a distinct connection between the consumption of the milk of certain cows and outbreaks of diphtheria among tho consumers. The peculiar featm-e of these outbreaks was the absence of any evidence which in any way connected the disease with antecedent cases in tho human subject, Later a disease of a catarrhal or pulmonary form among cats was apparently associated with diphtheria among human beings, and notably in children who nursed the sick cats. But in such instances it was gefierally left open to anyone to suspect that the people who suffered might have infected the cats. At any rate, there was no explanation of the origin of the cat disease. It may be observed that when Dr Ballard suggested a probable connection between some obscure disease in cows and diphtheria of man, bacteriology in this country had hardly been heard of; and the microscopic investigations relating to disease did not include any definition of the organisms in the products of the disease. Since that time an entire change lias taken place in the scientific position, and for some years past bacteria, as microorganisms are commonly called, have held a prominent position as causes of diseases, chiefly of contagious disease, although there is no reason why their influence in ordinary morbid processes should be questioned. Indeed, they may be said to have an important part tc play in all the changes which take place in dead and living organic matter ; one difficulty which the scientist has to deal with in his investigations into the history of disease producing microbes is their identification. It may be accepted as a fact, that from any organic substance a number of microbes may be obtained by cultivation in suitable media. The unscientific reader will understand what is meant by this when he is told that microbes belong to the vegetable kingdom, and like plants in general, they produce seeds, or spores, which cannot, of course, be seen without a high magnifying power, on account of their extreme smallness. In order to grow them, they must be sown in some medium in which there is organic matter for them to feed on. Meat broth, with or without gelatine, is used for the purpose; and to secure the growth of the microbes in an unmixed state, the medium is sterilised by heat, which kills all organisms already existing in it, and leaves a proper soil, in which, however, nothing can grow until it is planted. When the bacteriologist plants, by means of a fine wire, a minute quantity of some suspected substance from a diseased animal, he is said to inoculate the broth, or nutrient gelatine, and, as a result, he obtains an abundant growth of organisms of various sorts. Among them he may perhaps have the disease.producing microbe which he seeks, and his next Btep is to separate the various sorts and cultivate them by themselves, in order that he may test their qualities. To prove that a microbe has the power to cause disease, it is necessary to show that its introduction into the system of a susceptible animnl induces the symptoms and morbid changes characteristic of the disease, and further, the organism must be found-again in the diseased parts, and in some cases in all the organs of the body. A pure cultivation, for example, of the anthrax organism may be kept growing on gelatine for years, and at any moment a needle dipped in the cultivation may be used to puncturo the skin of a small animal—mouse, rabbit, or guinea pig with tho certainty that the inoculated animal will die in a few hours, and that after death the blood and every organ in the body will be found crowded with the peculiar organism, which may be used for further cultivation and inoculations, and always with the same result. Not many microbes exhibit the positive qualities of tho bacillus of anthrax; but among them the bacillus of diphtheria may claim to have disease-producing powers of a high order. It is true that its growth is limited to the part to which it is introduced ; but it seems to set up in tho part a peculiar action, resulting in the manufacture of a poison which infests the whole system and kills the animal. Post mortem examination proves that the microbe has not invaded the body generally, but has done its deadly work in the small space to which the diphtheritic membrane is limited. The rule of the localisation of the bacillus is open to exception, according to Dr Klein, in the case of the cow, the particular animal in which the distribution of the bacillus is likely to be attended with the most disastrous results. Dr Klein’s paper, ‘ On the Causes of Diphtheria,’ read before the Royal Society May 22, contains on account of some very important in*

vestigations, which may be summed up in a few words. Two healthy cows were inoculated with a culture of the bacillus derived from a case of diphtheria in man. Some local swelling occurred, but, after a week, gradually subsided. Meanwhile, the cows became ill, and during the illness both animals had an eruption on the teats and udders. One cow died on the fifteenth day, and the other was killed on the twenty-fifth day. A few days after inoculation milk was taken from a healthy teat of one of the cows, and the bacillus was obtained in large quantity by cultivation ; so that in this case the habit of the organism to keep to its place was departed from. When the milk of the inoculated cows was found to contain the germs of diphtheria, directions were given to throw it away—an order which was interpreted by the attendant to refer to the human race only, and he gave it to a number of cats which were in the institution wlieu tho experiments were performed, and’ the animals so fed became affected, and some of them died, with the characteristic indications of diphtheria. It may be presumed that the experiments will bo continued until some conclusion is arrived at as to tho origin of the diphtheritic condition in the lower animals. If cows are only infected by human agency, the fact will only indicate a calculable addition to the risks of spreading the disease by indirect means —a danger which may to some extent be guarded against; but should the evidence lead to the presumption of an independent origin of the disease in the cow, it will be difficult to provide a remedy for a risk so obscure unless some means could be devised for preventing the consumption of uncooked milk.—The Field.