Causes of Tumors. 333 



the liver produced bile in tliis position, (lenerall}- the secretions 

 of tumors are apt to be the seat of pathological changes, as ordi- 

 narily there are no channels for discharge in the growth and the 

 secretion therefore is stagnant; and moreover the function would 

 be more or less abnormal, because of the abnormal topographical 

 relations of the proliferated glandular epithelium, the failure of 

 complete differentiation of the cells, or the reversion of tumor 

 cells to embryonic type and the lack of relation with the nervous 

 system of the host of the tumor. 



There are conditions however under which the secretory pro- 

 ducts of a tumor are not devoid of value to the body, particu- 

 larly tumors of glands which produce internal secretions of im- 

 portance to metabolism and whose destruction would be ominous 

 to the well-being of the body, as the thyroid gland and pancreas. 

 The fact that growths from these glands may also produce 

 internal secretions may in some measure compensate for the 

 death or destruction of the organ by the tumor. 



[Of all the body functions, that of growth (and that is rather 

 a mere vital phenomenon and not a dift'erentiated function) is the 

 one which is best and most completely manifested, being in line 

 with the embryonic characteristics which tumors as a class 

 possess. The example of the performance of a function of value 

 to the economy selected by the author in the preceding para- 

 graph is practically the only one which may be named. The 

 fat which accumulates in a lipoma is of no service to the host 

 of the tumor even if he be starving; the connective tissue of a 

 fibroma is of no connective or supportive value, but rather a 

 continual source of annoyance from weight and pressure. Even 

 the function of growth, most nearly typifying natural energy, is, 

 as the author points out. irregular in the manner of its occurrence, 

 is without efficient organogenic power and especially abnormal in 

 that it has no definite period of cessation.] 



Aetiology of Tumors. — We possess but few facts and have but 

 a meagre idea about the mode of origin of tumors. Many the- 

 ories have been framed to explain the luxuriant growth of the 

 cells, but the diffiiculty of positive proof leaves us in uncer- 

 tainty between probabilities and theoretical dicta. Mere supposi- 

 tions that as the result of the action of a given stimulus this kind 

 or that kind of cells are excited into irrepressible multiplication, 

 revert to their embryonic characteristics or undergo biological 

 changes as expressed by the terms metaplasia or anaplasia, 

 are in no sense satisfying, but merely serve to conceal our igno- 



