86 Society for Experimental Biology and Medicine. 



of this tumor into other waltzing mice has been successful in one 

 instance. The growth in this case is relatively slow. A third sub- 

 cutaneous adeno-carcinoma, differing in structure from both of the 

 preceding ones, has been inoculated into a number of mice, which 

 are now under observation. 



Thus in the experimental inoculation of four spontaneous 

 tumors into other mice, a new growth has followed with one only. 



An important fact in this series is the relative frequency with 

 which single cases present more than one primary tumor. In 

 three mice there were in each two primary spontaneous tumors of 

 different types. In several other cases a primary tumor occurred 

 in a mouse in which there was also an inoculated tumor. 



The mice under observation are kept in small cages, which 

 are kept as clean as possible and scrubbed periodically with hot 

 water and soap. In the seventeen tumors, of this series, there has 

 been no definite indication of cage-infection. On the other hand 

 the frequency of tumors in certain families of mice has suggested 

 the possibility that heredity plays a part in the occurrence of 

 tumors. Certain families of mice, which are susceptible to the 

 inoculable tumors, have developed spontaneous tumors ; other 

 families, which are not susceptible to the inoculable tumors, have 

 never developed spontaneous tumors. Since heredity is unques- 

 tionably a factor as regards the growth of the inoculable tumors, 

 it should also be considered as a possible factor in the develop- 

 ment of spontaneous tumors. Breeding experiments have thus 

 far furnished results in accord with this hypothesis. 



Since it has been demonstrated that spirochete occur frequently 

 in tumors of mice, silver preparations have been made of several 

 of the tumors of this series, following the technic of Levaditti. 

 No spirochetal were found in the lympho-sarcoma, but they were 

 found in small numbers in the tumor of the Japanese waltzing 

 mouse. The skin covering this tumor had not ulcerated. 



Spirochetal were also found in the stroma of an inoculated 

 tumor of the Jensen strain. None were found in several human 

 cancers and in an actively growing sarcoma of a hen. 



Silver preparations were made of the tissues of several mice 

 which had no tumors. One mouse which had been twice inocu- 

 lated with the Jensen tumor, died six weeks after the last of the 



