38 WARFARE IN THE HUMAN BODY 



trophoblast is in a sense of alien origin, whereas ordinary 

 malignant growths are autochthonous. In this very fact 

 of partial alien origin lies support of the view suggested. It 

 is more than conceivable that the male element in the 

 zygote is here the earliest possible origin of malignant 

 energy. It would not be wholly surprising if future investi- 

 gation traced such cases to the peculiar energy of some 

 spermatozoa. The ease with which a sperm-cell enters the 

 unfertilized ovum might be a measure of the likelihood of 

 chorion-epithelioma, provided that the resistance of the 

 ovum were a measure of the general tissue resistance of the 

 maternal organism. But even granting that the alien, or 

 partially alien, origin of the trophoblast renders malignancy 

 more likely than with ordinary somatic tissues, it may be 

 replied, on the lines adopted at the beginning of this paper, 

 that all such tissues are, in spite of their symbiotic life, 

 fundamentally alien and hostile. A breakdown in their 

 relations as established by evolution may, and in many 

 forms of disease does, occur. By the study of the glan- 

 dular system the interdependence of all tissues is inferred. 

 There is, also, undoubtedly self-protection. " Thus far 

 and no farther " is embryological law. With deficient 

 inhibition we see this law abrogated. For in a new environ- 

 ment we may see any variation. Thus the polymorphism 

 of malignant epithelial cells described by E. H. Kettle is 

 just what might be expected on the loss of normal control. 

 The whole body is a group of organs and tissues which are 

 not always harmonious, and the behaviour of malignant or 

 benign aberrant tissue is by no means a phenomenon 

 standing by itself. Probably all tissues might become 

 malignant if they were as capable of free and rapid pro- 

 liferation as connective tissue and epithelium . Invasiveness 

 is natural to embryonic tissues. But have not embryo- 



