TUMORS. 299 



We have now reviewed a : series of conditions which appear more or 

 less directly to bear upon the origin of tumors ; general conditions, such 

 as age, sex, hereditary influences, etc. ; local conditions, such as congen- 

 ital or acquired malformations, injuries, long continued irritation, or 

 inflammatory processes. But when all these are taken into the account, 

 we do not appear to have gained a definite clew to the immediate actual 

 excitant of the new growths. Given any or all of the varied predispo- 

 nants, why do the cells, which under any of these favoring conditions 

 may have remained long inactive, and indeed usually do so, presently 

 begin to proliferate and continue this new activity beyond the limita- 

 tions of structural types or physiological correlation? It would appear 

 that either there are external excitants of cell growth, as yet unknown to 

 us, which suddenly become active, or else we are face to face with the 

 fundamental problem as to the nature of the normal physiological im- 

 pulses to cell growth and proliferation 1 and the restraining influences to 

 which these are subject. 



Micro-organisms as Excitants of Tumors. It is not surprising that 

 micro-organisms should have been thought of as possibly direct excitants 

 of tumors, especially in view of a certain crude analogy between some 

 phases of tumor growth and metastasis and some forms of infection with 

 metastasis. Bacteria of many kinds have in fact been frequently found 

 in tumors of many sorts ; but there is, in the opinion of the writer, no 

 conclusive reason at hand for the belief that they are ever of any signifi- 

 cance save as chance contaminations of vulnerable tissues or as incitauts 

 of secondary and complicating lesions. 



A great deal has recently been written about certain structures which 

 are not infrequently found in or between tumor cells, especially in the 

 carcinomata, and have been hastily assumed to be parasites. These cell 

 "inclusions" are for the most part larger or smaller rounded bodies (Fig. 

 134); with or without nuclei; sometimes with double contours, some- 

 times not ; usually sharply outlined against the cell protoplasm in which 

 they lie ; often crowding the nucleus to one side, often situated within 

 the nucleus, or apparently replacing it. Some of them are invaginated 

 epithelial or other cells, or cell nuclei which have undergone various 

 degenerative metamorphoses, fragmentation, etc. ; some of the question- 

 able structures appear to be the metamorphosed nuclei of the tumor cells 

 themselves. They may be single or there may be several in a cell. 

 Similar objects are to be found in other than tumor tissues. They are 

 readily stained, with varying degrees of intensity, by hpemotoxyliu, eosin, 

 safranin, or fuchsiu. There is in the writers' opinion no evidence either 

 that these are living organisms or that they have anything to do with the 

 origin of tumors. 



While coccidia or allied organisms with which these bodies have been 

 compared are capable of inciting the growth of a small amount of new 

 connective tissue and sometimes of epithelium, such growths are appar- 

 ently inflammatory in character as are those other new tissue formations 

 1 Consult the section on Regeneration, p. 94 



