64 



was closed at both ends and distended by a thin, watery pus into a 

 large sausage-shaped mass about the size of an index finger. The 

 opposite horn of the uterus contained six foetuses. A very curious 

 case was one in which four foetuses, each one a little less than an inch 

 in length, were found lying in the midst of a large, yellowish, putty- 

 like mass that distended one horn of the uterus into a balloon-shaped 

 mass about 3 centimeters in diameter. The f cetuses were partly dried, 

 and had evidently been dead for a long time. 



TUMORS. 



Tumors among rats and mice are not infrequent when these ani- 

 mals are kept in captivity, and the tumors of mice especially have 

 been made the subject of very extensive experiments for the pur- 

 pose of determining the mode of transmission, the question of immu- 

 nity, and other subjects that might throw light upon malignant 

 growths in the human family. White or tame rats have been much 

 less used than mice. However, it is interesting to note that the 

 earliest observations on the successful transplantation of a malignant 

 growth from one animal to another was that of Hanau (1), who 

 reported a carcinoma of the external genitals of a white rat and he 

 succeeded in transplanting this tum6r into other white rats. 



I shall not make any attempt to review the enormous literature 

 on tumors in tame rats and mice, but shall merely mention some 

 of the more important points that have been learned in an experi- 

 mental way in regard to this subject. The histological nature of the 

 tumors found in white rats was of particular interest, as we wished 

 to compare them with the tumors that have come under observation 

 among the wild rats in San Francisco. 



In addition to Hanau's case of carcinoma cited above the fol- 

 lowing tumors of white rats are mentioned. Herzog (2) observed a 

 cystic sarcoma of the neck of a white rat. Loeb (3) mentions three 

 tumors of white rats; an adenoma in the mammary gland, an adeno- 

 carcinoma of the pancreas, and a carcinoma of the thyroid. Flexner 

 and Jobling (4) report a mixed cell sarcoma of the seminal vesicles of 

 a white rat. This tumor upon transplantation showed a marked 

 tendency to produce metastases. Gaylord and Clowes (5) report 

 cases of fibrocarcinoma of white rats arising apparently from infected 

 cages, and they present evidence that in certain breeding establish- 

 ments carcinoma is endemic among the white mice. Spontaneous 

 tumors are nmch more frequently met with in mice than in rats, and 

 a number of epidemics of malignant growths have been observed 

 among mice in captivity. 



Tyzzer (6) found in a mouse a primary adenocarcinoma of the 

 lung and an adenoma of the kidney. Loeb (7) found that upon the 

 transplantation of a pure gland-like tumor (carcinoma) which origi- 



