40 STUDIES l\ [MMUNITY. 



each guinea-pig received i\, of a culture. The next morning the 

 guinea-pigs that had received the edema fluid and the normal rabbit 

 serum respectively were found dead; the guinea-pig that had 

 received preventive serum was slightly sick, but soon recovered. 

 There were a Dumber of leucocytes in the peritoneal exudate of the 

 guinea-pig that had received the edema fluid, but very few in the 

 control thai had received normal rabbit serum. 



Even when the dose of culture used is very large or the guinea- 

 pigs are very small, so that the immunity conferred by the serum 

 is not perfect, there is always to be noted a distinct delay in the 

 death of the animal receiving the preventive serum over the other 

 two. For example: 



Experiment 11. Guinea-pig "A" (245 grams) received 0.2 of 

 a cubic centimeter of serum; guinea-pig "B" (255 grams), 0.2 of 

 a cubic centimeter of edema fluid. The following day these animals 

 and a control "C" (339 grams) were given each tV of a culture. 

 The following day the guinea-pig injected with edema and the con- 

 trol were found dead; the guinea-pig injected with preventive 

 serum did not die until the following day, which is a considerable 

 delay when one considers the usual rapid evolution of the perito- 

 nitis caused by the cholera vibrio. In such instances an exami- 

 nation of the peritoneal exudate is interesting. The exudate in the 

 control is always found to be poor in leucocytes and over-running 

 with vibrios. The exudate from the guinea-pig that has received 

 edema fluid always contains considerably more cells than the control, 

 but very much fewer than does the exudate of the animal that has 

 received serum ; and in this latter animal, too, the vibrios are very 

 much fewer in number. The proportion of leucocytes in the exudate 

 indicates the relative resistance of the individual. 



Experiment 12. A rabbit had been well vaccinated against 

 the Massaouah organism. Eighteen days after the last injection 

 an edema was produced. The blood contained 5000 leucocytes 

 per c.m.m. 



(a) Rather large guinea-pigs were used. No. 1 (455 grams) 

 received 0.3 of a cubic centimeter of edema fluid; No. 2(430 grams), 

 0.3 of a cubic centimeter of serum ; on the following day these two 

 animals and a control, No. 3 (450 grams), received each iV of a 

 culture. The control was the only one to die. 



