312 Chapter X 



as these I considered that I was justified in formulating the following 

 conclusion at the end of my memoir : " From the facts I have de- 

 scribed, taken collectively, we may draw the conclusion that the 

 preservation of unvaccinated rabbits treated with serum is due to a 

 superactivity of the phagocytic defence ; and it is allowable to 

 express the opinion that the protective serum of hog cholera acts 

 in rabbits by stimulating the phagocytes, rendering them less sensi- 

 tive to the toxins, and by stimulating them in their struggle against 

 the bacteria" (p. 310). The facts since collected by various observers 

 fully justify this hypothesis. Amongst the other micro-organisms 

 against which a rapid immunisation has been obtained by means 

 of serum, we must cite the cocco-bacillus of bubonic plague. 

 Numerous experiments, carried out on several species of animals, 

 have shown that antiplague serum markedly augments the phago- 

 cytic reaction. 



[328] In the group of the cocci, the streptococci have been specially 

 fully studied from the point of view now under discussion. As 

 already stated in another chapter, success has been attained not only 

 in thoroughly immunising several species of animals against this 

 dreaded micro-organism but active serums have been obtained 

 capable of conferring distinct and certain immunity. The protective 

 action of Marmorek's serum, prepared at the Pasteur Institute, has 

 been specially carefully studied. This serum is obtained from horses 

 that have received numerous injections of various races of strepto- 

 cocci pathogenic for animals and for man 1 . At Lou vain, Denys and 

 his pupils prepared several other antistreptococcic serums and studied 

 their protective effect on laboratory animals. 



In collaboration with Leclef, Denys 2 began by vaccinating rabbits 

 against streptococci and studied the mechanism of the immunity 

 obtained in these animals. A summary of their researches will be 

 found in the eighth chapter. Denys and Leclef considered that the 

 serum of vaccinated rabbits intervenes in two ways, first by directly 

 hindering the multiplication of the streptococcus and then by exalting 

 the activity of the leucocytes. They applied these results to the case 

 in which immunity is conferred upon normal rabbits by the inter- 

 vention of the serum of the vaccinated rabbit, but they were unable 

 to furnish any data bearing directly on this immunity. Somewhat 



1 Marmorek, Ann. de I'lnst. Pasteur, Paris, 1895, t. ix, p. 593. 



2 La Cellule, Lierre et Louvain, 1S95, t. xi, p. 175, and Bull. Acid. roy. de med. 

 de Belg., Bruxelles, 1S95. 



