4 2 



Scientific Proceedings (26). 



a capsule consisting of an outer fibrous layer, and an inner one 

 made up chiefly of round cells, or else the round cells invade the 

 implanted tissue. One is impressed with the great amount of 

 organization going on around the implanted pieces. On the other 

 hand, the pieces themselves seem to retain the cell structure much 

 longer than is usual in other animals. 



It seemed interesting to investigate whether the white rat will 

 also react differently from other animals to an introduction of an 

 irritating foreign body. 



An emulsion of aleuronat produces, in the ordinary laboratory 

 animals, an abscess, when injected under the skin, and empyema, 

 when injected into the serous cavity. In nine rats an emulsion of 

 aleuronat was injected under the skin, and in each animal there de- 

 veloped in the place of injection a freely movable tumor the size 

 of a small nut, which on examination proved to be a cyst filled 

 with thick cheesy detritus. In only two animals did the skin be- 

 come eroded ; in the others the growth retained the same size 

 during two to three weeks. 



In six white rats I introduced into the peritoneal cavity one or two 

 triturate tablets of aleuronat. The animals were killed in three days 

 to two weeks after the operation. At the autopsy there was found 

 in the place of each tablet a little growth of white grayish color, 

 the consistency of a granulation, loosely adherent to the omentum, 

 occasionally with some cheesy detritus in the center. Microscop- 

 ically the growth consists of a conglomeration of round cells and 

 leucocytes towards the center, and round cells and some beginning 

 of fibrous connective tissue formation towards the periphery. 



While even this last named formation is not a tumor in the 

 true meaning of the word, but a connective tissue reaction to an 

 irritation, it seems to be clear from all these experiments that the 

 reactive cell proliferation and cellular organization is much more 

 extensive in a white rat than in the other laboratory animals. On 

 the other hand the absorption of the implanted tissue is a great 

 deal slower, consequently there is a better chance for the implanted 

 cell to proliferate and for the implanted tissue to grow. Whether 

 there is still a qualitative difference between a tumor cell and a 

 normal tissue cell, or conditions may be found under which nor- 

 mal cells will acquire the power of limitless proliferation, for the 



