126 CARNEGIE INSTITUTION OF WASHINGTON. 



ney, and spleen. Nodules of tumor cells occurred in these organs surrounded 

 by normal tissue. In some cases it could clearly be seen that the tumor 

 cells surrounded or lay close to a blood-vessel." 



In these cases, therefore, it seems clear that a transfer of minute 

 groups of cells or of single cells has taken place through the blood- 

 system. An interesting line of investigation concerning the course 

 and mechanics of metastasis is thus suggested. 



Spleen implants in mice of different strains. — A series of experiments 

 has been conducted by Dr. Little and Miss B. W. Johnson to investi- 

 gate the method of inheritance of favorable or unfavorable reaction to 

 subcutaneous implants of spleen tissue. The material used for this 

 consisted of two races of mice. The first of these was a strain of Japa- 

 nese waltzing mice which had been subjected to the closest inbreeding 

 for approximately 15 years. This is the Lambert strain already de- 

 scribed in connection with work on inheritance of susceptibility to 

 transplantable tumors. 



These animals are, as a result of the long-continued inbreeding, 

 remarkably uniform genetically. It is a well-established fact that if a 

 piece of the spleen of a mouse be transplanted subcutaneously in the 

 same animal (autoplastic implant), the implant will persist and a blood- 

 supply will be established. In other words, the animal does not treat 

 the implant as a foreign body, but attempts to nourish it even in an 

 unaccustomed position. 



If a piece of the spleen of another unrelated animal of the same spe- 

 cies is placed beneath the skin (homioplastic implant), the host usually 

 reacts unfavorably to the implant, treating it as a foreign body, and by 

 leucocytic action or invasion of connective tissue succeeds in eliminat- 

 ing the implant. 



Theoretically, when animals have been inbred for a considerable 

 period they become, as above stated, remarkably homogeneous genet- 

 ically. This should mean that when a homioplastic implant is made 

 between two such genetically similar individuals the conditions will 

 approximate or be equivalent to those of an autoplastic implant. 

 Work already reported by Little and Tyzzer on the transplantable 

 tumors J. W. A. and J. W. B. shows that the Japanese waltzing mice 

 of the Lambert strain fulfill the requirements of genetic uniformity 

 to a marked degree by growing subcutaneously implants of the tumors 

 which originated in animals of that race. 



When the Japanese tumors were transplanted into individuals of an 

 unrelated race of albino mice, an occasional individual supported the 

 implant for a short time, but the final result was in every case negative. 



If the Japanese mice are essentially homogeneous genetically, the 

 hereditary factors carried in their gametes should be essentially the 

 same. Implants of Japanese-mouse tumor in first-generation hybrids 

 between Japanese and albino mice grew in all cases. This showed 



