44 Society for Experimental Biology and Medicine. 



Inasmuch as it may be said that the plasmolyzed material does 

 not represent a true solution, a series of experiments were made 

 with the filtered (Berkefeld) plasmolyzed liquid. While these ex- 

 periments go to show that immunity can probably be induced by 

 such filtered soluble products, they are not as decisive as they 

 should be and for that reason will have to be repeated. The chief 

 reason for this uncertain result is the rather frequent failure of the 

 control rats to develop infection. Although young rats (50-80 

 grams) were used to guard against previous infection with trypan- 

 osomes, it is certain that a large percentage of the rats, as pur- 

 chased on the market, have acquired an immunity against Tr. Lewisi. 

 That the immunity encountered is really acquired and not natural 

 is shown by the fact that we have many times isolated Tr. Lewisi, 

 by means of the cultivation method, from rats which on repeated 

 examination were found to be free from parasites and hence were 

 supposed to be normal. 



33 (176) 



On secondary transplantation of a sarcoma of the rat. 

 By SIMON FLEXNER and J. W. JOBLING. 



[From the Rockefeller Institute for Medical Research^ 



At a meeting of the Society held on, October 17, 1906, we 

 presented specimens of a sarcoma of the rat which was being 

 transplanted successfully. 1 In the course of the transplantations 

 the percentage of successful issues has reached approximately one 

 hundred. In many series, every transplanted fragment developed 

 into a tumor, and in none of the latter series has the percentage 

 of " takes " fallen below ninety. The tumor having reached this 

 maximum of infectivity, it was thought desirable to ascertain to 

 what extent secondary transplantation would succeed. The 

 method followed was to inoculate rats, in which a tumor nodule 

 was already present, with another fragment of the tumor tissue. 

 The second inoculation was made, as a rule, on the side of the 

 body opposite the existing nodule, but in a few cases it was made 

 in the tissues adjacent to the first nodule. After the second 

 growth had developed to the size of a pea or bean, the rats were 



'This volume, p. 12. 



