34 WARFARE IN THE HUMAN BODY 



these differences exist, and we shall then be able to class 

 malignancy among other phenomena of normal and 

 abnormal growth. The attribution of malignancy to foods 

 is possibly not without value, if it leads to a diet which is 

 not irritating to the intestinal canal, and the fact that 

 salmon or trout fry, when fed abnormally on hog's liver, may, 

 it seems, suffer from an overgrowth of thyroidal tissue, which 

 later may become malignant, is of importance ; but we are 

 still as far as ever from the knowledge of causes which leads 

 to explanatory classification. It appears that all these 

 views are true as far as they go. If it can be shown that 

 they all point in one direction, we should not be far from 

 the truth. 



There are, however, other theories to be taken into 

 account, which appear of greater value, since they are more 

 than re-statement, and seek explanation in the nature and 

 functions of the very tissues which become abnormal. 

 Such endeavours take into consideration not only pathology, 

 but physiology as well. If it is said, by the way, that there 

 is no greater hindrance to scientific advance than the 

 separation of physiology and pathology, few, who are not 

 specialists in either branch of learning, will be found to 

 deny it. The opinions, for they are little more, of Thiersch 

 and Waldeyer, have at any rate the advantage of contact 

 with the physiological side of the problem. Thiersch 

 held that with advancing age the connective tissue ceased 

 to be able to hold the epithelium in check. It was a 

 brilliant guess, but it failed to account for carcinomas in the 

 young, nor does it in any way explain sarcomas. Yet 

 how near the truth it was may possibly be shown later, 

 though, according to Bainbridge, the modern view of the 

 function of epithelium during development is that it 

 determines the character of the connective tissue, and 



