

vii INFECTION OF ANIMALS WITH PLAGUE 189 



Guinea-pig No. 14 was injected with emulsion of 

 the " sand-plague " organs. 



Guinea-pig No. 15 was injected with emulsion of the 

 " earth-plague " organs. 



Guinea-pig No. 14 remained without swelling, and was 

 altogether unaffected ; it was killed on August 2, and 

 gave totally negative result as regards plague. But 

 guinea-pig No. 15 was distinctly ill on July 26 and had 

 bubo. It was killed on the same day, and showed the 

 following appearances : necrotic bubo ; spleen, liver, and 

 lungs crowded with necrotic nodules and patches. Film 

 specimens and cultures of the bubo, spleen, and lung 

 yielded crowds of B. pestis. 



Fig. 24 shows, in a section under a low power, a 

 necrotic nodule of the spleen containing aggregations 

 (dark) of B. pestis ; these aggregations being in reality 

 networks of blood spaces of the pulp tissue. 



Fig. 21 shows, in a section (x 100) through the lung, 

 one of the nodules (this being in reality an infundibulum 

 with its alveoli) all blocked with masses (dark) of 

 B. pestis. 



From this experiment it appears, therefore, that while 

 "sand-plague" material dried for fourteen days at the 

 ordinary temperature was barren of infective power, 

 " earth -plague " material still retained its efficacy. The 

 former was therefore discarded, but the latter was retained 

 for further experiment. 



Experiment 8. — With emulsion of the same " earth- 

 plague" material now dried for three weeks, guinea-pig 

 No. 16 was injected on July 28. This animal appeared 

 unaffected on August 3, i.e. after six days. It was killed 

 and found in all respects normal. 



