STUDIES ON THE SERUM OF VACCINATED ANIMALS. 21 



at the same time with two more or less completely bactericidal 

 liquids, a comparison may be drawn as to their bactericidal value 

 according to the number of colonies that grow on the respective 

 plates. It is obvious that the same emulsion of organisms is used 

 for each series of tubes, and the same platinum loop is used so as to 

 render the quantities of liquids strictly comparable. A table may 

 be made indicating the number of colonies which have developed 

 on each plate and the time after inoculation at which the trans- 

 plantations were made. With this explanation we offer the protocol 

 of an experiment made for the purpose of comparing the bactericidal 

 properties of the blood and of the peritoneal exudate from an animal 

 vaccinated against cholera. 



EXPERIMENT 2. A rabbit weighing 1720 grams had been well 

 vaccinated against the vibrio of Massaouah; two weeks after the 

 last injection a small amount of blood was drawn, from which was 

 obtained serum I; two sponges previously washed and boiled in 

 water, sterilized, and dried (June 14, 1894), were then placed in the 

 peritoneal cavity. They were removed the next day and found 

 to be filled with fluid that was squeezed into two sterile vessels. 

 (Exudates I and II.) The leucocytes in this fluid were infrequent 

 (about 500 to the c. mm.) and quite a number of them adhered to 

 the sponge. A second specimen of blood was then taken (serum II) 

 which was found to contain 8200 leucocytes. One cubic centimeter 

 of each of the samples of serum and of the peritoneal exudates was 

 placed in a tube and their respective bactericidal powers against the 

 vibrio of Massaouah determined by the plate method. Since it had 

 already been determined that the serum was rather strongly bac- 

 tericidal, a relatively large amount of this culture was planted each 

 time (a loop of a vigorous agar culture, 24 hours old, suspended in 

 5 c.c. of salt solution of 0.6 per cent). The following plates were 

 made at intervals indicated in the table: 



NUMBER OF COLONIES. 



