Veterinary Notes for Horse Owners Book

Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: CHAPTER III. Immunity And Heredity. In this chapter I propose to glance at the respective theories Of immunity and heredity, both of which have a large influence on disease. Susceptibility, I need hardly say, is the opposite of immunity. Immunity. Immunity is the power which an individual or a species has to resist the attack of a disease. It may be racial, individual, or acquired; and may be absolute or comparative. for instance, horses possess racial immunity agaiubt the scarlet fever of man and the pleurp-pneumonia of cattle. Men are immune from strangles; and ruminants, from glanders. Among every species of animal, we find individuals which are more or less refractory to the inroads of a disease to which their fellows show marked susceptibility. The man, horse, or ox which has had one attack, respectively, of smallpox, strangles, or jileuro-pnoumonia, will have acquired more or loss immunity from a second attack. As possessors of comparative immunity, I may cite Algerian sheep, which are refractory to anthrax, when inoculated in the usual way ; but prove susceptible to it when the dose of the virus is largely increased. Dogs rarely contract tetanus; horses, on the other hand, are very susceptible to it. On page 125, I allude to the accidental immunity of the carnivora to actinomycosis. The immunity of fowl against anthrax appears to be due to their high internal temperature (107.5 I'.i. for Pasteur has proved that if a fowl be inoculated with anthrax, and is then placed and kept in water at a temperature of 77 F., so as to considerably reduce its internal heat, it will die of anthrax in about a day and a half. The nature of the lesions set up in the tissues by certain diseases, greatly affects comparative resistance. Thus, in a man who has been inocula...Read More