_ cowtr| bption to the study of serum-therapy in diphtheria. 663 
toxine will be given. The animals must be frequently weighed 
and the injections be interrupted if they lose weight, otherwise 
t ey get into a cachectic state which ends fatally. In these 
experiments we gain time by going slowly. 
Dogs have furnished to some experimenters, among whom 
ardach and Aronson, a very active serum. Sheep, especially 
goats, are very sensitive to the action of the diphtheritic 
poison. 
The immunization of females which give a good deal of 
mi such as goats and cows, presents a peculiar interest, since 
.bhrlich has shown us that'the antitoxine passes in the milk. A 
milch cow, that is well immunized, is a source of antitoxine 
Its milk is, of course, far less active than its serum, but the 
antitoxine which it contains may be condensed within a small 
volume, and hence is a good primary material for the prepara* 
tion of antitoxine. 
Of all animals capable of furnishing large amounts of anti- 
diphtheritic serum, the horse is the easiest to immunize It 
bears the toxine much, better than the other animals we have 
mentioned. We often see horses that have received from the 
first a dose of two to five c. c. of strong toxine, injected under 
the skin, and which present only an ephemeral febrile move¬ 
ment and a local oedema which rapidly disappears. The ass 
also bears the toxine well. If we admit, with Behring, that the 
serum of an animal is all the more antitoxic and he shows the 
greater sensitiveness to the toxine, the choice of the horse may 
appear as a bad one. But, since 1892, we began to immunize 
horses against diphtheria because, following the results obtained 
by Roux and Vaillard with tetanus, we knew that serum of 
horses is inoffensive for animals and for men, even when in¬ 
jected in large amounts. When injected under the skin it is 
immediately absorbed, and without local reaction. Moreover, 
nothing is easier than to take from the jugular vein of a horse, 
as frequently as it may be desired, and perfectly pure, large 
quantities of blood from which a perfectly limpid serum may be 
removed. We have some horses from whose jugulars, by 
