March 3, 1916] 



SCIENCE 



297 



exclude the possibility that certain other 

 organisms might play a certain role. We 

 know that microorganisms can call forth 

 cell multiplication in plants and animals. 

 In plants, certain bacteria can produce, as 

 has especially been demonstrated in the 

 case of the crowngaU by Erwin F. Smith, 

 tumor like proliferation — a result depend- 

 ing in this case not merely on the kind of 

 stimulus, but also on the particular system 

 on which the stimulus acts. In this con- 

 nection we might also mention a number of 

 extremely interesting cases in which various 

 investigators saw the transformation of 

 normal into cancerous tissues, subsequent 

 to contact with cancerous tissue of another 

 kind, but in the same individual. I re- 

 ferred above to an observation of this char- 

 acter in which we found skin to become 

 cancerous under the influence of an adeno- 

 carcinoma of the mammary gland. Sim- 

 ilarly, in contact with carcinoma, connec- 

 tive tissue may become sarcomatous. Such 

 tumors we called combination contact 

 tumors. In such a carcinosarcoma in a 

 Japanese mouse which we studied experi- 

 mentally, we found that the carcinomatous 

 and sarcomatous components followed the 

 same variation curve of growth energy in 

 succeeding generations. This suggests the 

 identity of the agent which causes the pro- 

 liferation of both tissues and the depend- 

 ence of the variation in growth upon the 

 variation in the activity of the agent. The 

 agent transferred from one tissue to an- 

 other might be a chemical substance — an 

 explanation first suggested in the case of 

 the sarcomatous transformation of the 

 stroma by Ehrlich and Apolant — or it 

 might be a microorganism. Even under 

 normal conditions there are indications 

 which point to a chemical influence exerted 

 by one tissue upon another. In this man- 

 ner we interpreted the difference in cell 

 activity in the connective tissue of the 



mucosa in certain organs near the epithe- 

 lium on the one, and near the submucosa 

 on the other hand. The different effect 

 exerted by the tissues of different indi- 

 viduals upon the activity of the fibroblasts 

 of the host also points to such a conclusion 

 (different effects of auto- and homiotrans- 

 plantation). 



The very important results of Peyton 

 Rous are worthy of especial consideration. 

 This investigator, working with fowls and 

 employing methods which in the case of 

 mammalian tumor had not led to positive 

 results in the hands of earlier investigators, 

 was able to separate by filtration and other 

 means the causative agent from the sar- 

 coma cells with which it was associated. In 

 this case, we might have to deal either with 

 filterable microorganisms, or again with 

 chemical substances. If we accept the latter 

 alternative, we would have to assume that 

 the same substance that initiated the can- 

 cerous cell proliferation in normal cells 

 would, after the change has once been ac- 

 complished, be perpetually newly formed 

 within the proliferating cells. This condi- 

 tion would in some respects be comparable 

 to an autokatalytic process.* The cancer- 

 ous equilibrium would represent a condi- 

 tion in which this growth substance is either 

 produced in a larger quantity than it exists 

 in normal cells, or is entirely formed de 

 novo. It seems furthermore that no anti- 

 body is produced in the body-fluid against 

 this substance. These substances do not 

 seem to be separable from the cells in all 

 fowl tumors, and the kind of fowl tumors 

 in which a separation can not be accom- 

 plished behave in this respect like the mam- 



* Certain analogies between growtli curves and 

 autokatalytic processes have formerly been pointed 

 out by Jacques Loeb, W. O. Ostwald and T. B. 

 Robertson. In the case of fowl tumors we would 

 have in addition to deal with the new formation 

 within the tissue cells of a substance carried to the 

 tissues from the outside. 



