ABNORMAL GROWTH. TUMOURS 267 



rise to a secondary tumour. This would be a potential 

 Individual, whereas the primary tumour would only be a 

 small part of an Individual — the Individual attacked. 



These presumptions involve us in a strange state of 

 affairs. The body is attacked by an unnaturally arrested 

 part of itself which has escaped arrest ; and this part, 

 owing to the complete absence of control and guidance, 

 develops as an amorphous parasite, capable of forming 

 sexual elements and originating a new tumour as a tumour- 

 Individual. In this connection it seems just possible that 

 the so-called " cancer-bodies " discovered some years ago, 

 and considered by some observers to be parasitic in nature 

 and possibly causal agents of the disease, may be " tumour- 

 gametes." 



At the same time, there is no reason to doubt that a 

 primary malignant tumour may give rise to a secondary 

 one by vegetative production, and that tumour cells which 

 are not " gametes " may be separated from the original 

 mass and carried to new situations ; a species of trans- 

 plantation by cuttings. 



We may believe that early unnatural arrest does occur 

 in the developing embryo, for congenital moles and warts 

 can be explained in no other way. Moreover, these little 

 masses of unnaturally arrested cells not infrequently escape 

 from arrest and give rise to malignant growths, usually 

 sarcomatous, but at times epitheliomatous. 



It will be observed that this theory that benign and 

 certain malignant tumours are exhibitions of Escape from 

 Unnatural Arrest is practically Conheim's theory, and that, 

 like his, it does not explain the origin of all tumours. But 

 Unnatural Arrest is only one form of arrest, and it is with 

 the help of its opposite, Natural Arrest, that our theory is 

 made all-including. 



Tumours whose Origin is Due to Escape prom 

 Natural Arrest. 



Such tumours are the product of cells composing normal 

 differentiated tissues which exhibit the final arrest charac- 

 teristic of adaptation to special function. They do not seem 

 to arise so spontaneously as the tumours which have just 



