65 



nated in the submaxillary gland of a Japanese mouse both carcinoma 

 and spindle-cell sarcoma were developed, and this observation, that 

 transplanted tumors may give rise to a different histological growth 

 from that which was transplanted, has been made by others. Tyzzer 

 (8) reports 20 spontaneous tumors in mice. Of these tumors 12 

 were papillary cyst-adenomas of the lung and were mostly very 

 minute, some of them microscopic; 2 were cyst-adenomas of the 

 kidney; 2 lymphosarcoma, 1 of the groin and 1 of the mediastinum, 

 and 4 were adenocarcinoma. These 20 spontaneous tumors occurred 

 in 16 mice, 4 of them having tumors of 2 different types. Ehrlich 

 and Apolant (9) record the occurrence in a white mouse of a mixed 

 tumor (carcinoma sarcomatodes). Saul (10) mentions spontaneous 

 papillary adenocarcinoma and teleangiectatic carcinoma both in the 

 mammary glands of mice. 



Saul showed that by planting the common liver worm of the rat 

 (Cysticercus fasciolaris) subcutaneously in a mouse he was able to 

 develop a tumor which partook of the nature of a malignant (carci- 

 nomatous) growth. It will be seen by an examination of the data 

 presented below relating to spontaneous tumors in wild rats that a 

 considerable number of them have been associated with the pres- 

 ence of the parasite Saul used in his experiments. He also states (11) 

 that Borrel found worms or their remnants in malignant tumors of 

 mice. 



When metastases occur in mouse tumors the most usual seat of the 

 secondary growths is in the lungs, thus Tyzzer (12) observed metas- 

 tases in 4 cases out of 73 mice inoculated with the Jensen tumor. 

 He demonstrated that the metastases took place by the blood vessels, 

 not by the lymphatic channels, although the tumors were of a car- 

 cinomatous nature. 



Simon (13), who reviews the subject of mouse tumors with special 

 reference to the subject of immunity, remarks that mouse carcino- 

 mata, although found most frequently in old females, when trans- 

 planted grows equally well in males, and better in young than in old 

 animals. It has been found by some observers that a rat or a mouse 

 unsuccessfully inoculated with a strain is thereafter immune, to even 

 the most virulent strain. 



Haaland (14) and other writers have found a marked variation 

 in the susceptibility of different races of mice to mouse carcinoma. 



Ehrlich (15) and his co-workers Apolant and Haaland have re- 

 corded many experiments in transplantation of tumors of mice. They 

 have demonstrated that moderate heating of a mouse tumor length- 

 ens the incubation period, diminishes the number of successful 

 transplantations, and brings about certain changes in the histology 

 of the tumors reproduced. 

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