vii INFECTION OF ANIMALS WITH PLAGUE 171 



B. pestis. These bacilli could be traced in almost con- 

 tinuous masses (see Figs. 80 and 81) into the villi, into 

 the lymph spaces of the mucosa around the Lieberkiihn 

 crypts, and into the lymph vessels of the submucosa 

 around and between the lymph follicles. The mesenteric 

 glands were literally crammed with B. pestis forming 

 denser masses corresponding to the subcapsular and 

 medullary lymph sinuses. 



Experiment 7. — Having thus satisfied myself that 

 rats, mice, and guinea-pigs can be infected with plague by 

 feeding them on old and drying gelatine and agar cultures, 

 and that the intestines (ileum and Peyer's glands) of the 

 experimental animals demonstrate in unmistakable manner 

 the exact place where infection occurred, I directed my 

 attention to similar feeding experiments with grain, i.e. 

 with wheat and rice, which, having been mixed with 

 minced plague organs of guinea-pigs or rats, or with 

 gelatine cultures, had been allowed to dry. It is obvious 

 that these further experiments more nearly represent con- 

 ditions to which rats may become subjected as it were 

 naturally. 



The bubo, spleen, liver, and lung of a guinea-pig that 

 had died of plague after subcutaneous injection (guinea- 

 pig No. 9 of experiment 4) were, on June 6, finely minced, 

 and then well mixed in separate plate dishes, partly with 

 wheat, partly with rice. The two lots were placed over 

 sulphuric acid to dry. On June 7, i.e. after twenty-four 

 hours, the materials were found well dried, and were now 

 used for feeding. 



One dish (wheat and organs) was supplied to two rats 

 in one cage, the other dish (rice and organs) to two other 

 rats in a separate cage. Thus : — 



