Causes of Tumors. 339 



they were transplanted, continued to grow and form tumors of 

 the size of walnuts, growths of considerable size wdien that of 

 the experimental animal is taken into consideration.* Earlier 

 than this Hanau had succeeded in transferring an unquestionable 

 skin cancer of one rat to other rats wath similar results (in peri- 

 toneal cavity) ; and L. Loeb and Velich have successfully trans- 

 planted rat sarcomas, and Aloran has transplanted adenocarcin- 

 omata of a white mouse a number of times. [Still more recently 

 L. Loeb has carried an adenocarcinomatous tumor of a Japanese 

 dancing mouse through a number of generations, eventually find- 

 ing a change in the nature of the tumor which took on the histo- 

 logical characteristics of a spindle cell sarcoma. Other investi- 

 gators have described similar success in transplantation ; and 

 Loeb's instance of change in the tumor characteristics is not an 

 isolated one.] (Attempts to transplant sarcomas and can- 

 cers in dogs undertaken as much as ten years ago by Piitz and 

 other investigators have thus far failed.) The point of special 

 interest in Jensen's studies is the discovery that it is possible, 

 by special methods of implanting the tumor cells, to render the 

 diseased mice immune so that the tumors, which are present in 

 them and which are ordinarilv fatal, disappear and the subjects 

 recover. Jensen brought about this result in two ways, first by 

 treating the diseased mouse wath its own tumor cells, substances 

 developing in consequence in the blood (cytotoxins), which in- 

 hibited further extension of the tumor cells at the original site 

 (v. Chapter on Immunity) : and second by repeated introduction 

 of the tumor cells into rabbits (not susceptible to the mouse 

 carcinoma) he obtained a serum wdiich manifested specific cyto- 

 toxic action. [In a similar set of transplanted adenocarcinomata 

 of mice Gaylord found that some of the affected individuals re- 

 covered naturally, their tumors after more or less growth under- 

 going atrophy and disappearing. From such individuals he ob- 

 tained a serum which, when introduced into mice with marked 

 tumor growths, uniformly caused their disappearance by its 

 cytolytic power.] 



The tissue of tumors isolated from the body will retain its vitality at 

 a temperature of from i°-3° C. for about eighteen days, at room tempera- 

 ture for about twelve days, but at body temperature for scarcely twenty- 

 four hours. This difference is supposed to be due to the cells passing 

 into a sort of resting condition at the lower temperatures, while at the 

 body temperature they cannot avoid metabolism. 



♦For details v. Centralbl. f. Bakteriol. u. Par-asitenkiaulc, 1903, No. 1, ;>^XX!V 

 Pd. 



