52 WARFARE IN THE HUMAN BODY 



tuting a different environment. Further investigation will 

 almost certainly show that there is some reaction differ- 

 ence in the region of the femur when compared with that 

 of the tibia. The comparative immunity of joints from a 

 burrowing sarcoma supports the view that some tissues have 

 a more powerful resistance than others. It may be that the 

 great resistance of cartilage is due to its lack of channels ; 

 but it is far more likely that it is due to the cell products 

 of its closely arranged cells. In studying the various types 

 of malignancy we cannot but be struck by the varying 

 amounts of normal, or fairly normal, connective tissue 

 about them. That the small, round-celled sarcoma should 

 be more deadly than most of the other varieties is what 

 would be expected from the scantiness of the still growing or 

 surviving stroma. Such varieties as are more difficult to 

 distinguish from normal cells seem obviously those in 

 which the whole of the normal inhibition of the environ- 

 ment has not been overcome. These are points in which a 

 considerable knowledge of biology might be of assistance to 

 pathologists. 



While it is impossible to deal here in detail with every 

 kind of tumour, something may be said of embryomas and 

 their malignant forms. Obscure and difficult as the subject 

 is, there seems reason to believe that when it is understood 

 many of the basal problems of biology will be solved with 

 it. That they are due to some ovum, or embryonic ovarian 

 tissue, developing parthenogenetically, seems more than 

 likely. Shattock's remarkable paper on these tumours 

 supports the view that embryonic ova may be fertilized by 

 errant spermatozoa ; but there are many reasons for coming 

 to the conclusion that an embryonic " rest " may develop 

 without such assistance. Such views do not account for 

 infantile feminine or testicular embryomas. It is more 



