82 WARFARE IN THE HUMAN BODY 



is a big subject, not to be enlarged on here; but there still 

 remains much work to be done as to the indirect influences 

 of diseases, infections, and otherwise, upon physical and 

 cerebral development. It may be suggested that the 

 acuity of sensation and perception of those affected, but 

 not disabled, by tuberculosis and the slow acquisition of 

 immunity, may have modified human character to a 

 marked degree. 



It can even be shown that disadvantageous variations 

 actually become permanent racial characters. We may 

 consider hernias. During the processes of evolution, a 

 mammalian hernia seems to have occurred almost univer- 

 sally, and to have established itself as normally physio- 

 logical. The tunica vaginalis of the testis is actually part 

 of the original peritoneal sac, as can be seen in the embryo. 

 This was, of course, observed by John Hunter. During 

 foetal life it is separated from the parent sac. In whatever 

 sense we now call such a change physiological, it seems 

 impossible to regard it as originally anything but patho- 

 logical. I certainly do not know how we can describe the 

 scrotum as anything else than the coverings of an evolu- 

 tionary hernial sac, which is not only of no advantage, but 

 a positive danger to most male animals. This view has been 

 supported by Bramann. In some, the pigs for instance, 

 the testicles do not descend into an external pouch, but 

 are supported and protected by the normal skin tissues, 

 not by a thinned and delicate integument of later develop- 

 ment like the scrotum, a tissue still scantily supplied 

 with the non-striated muscular fibres which might have 

 reinforced it, and are, perhaps, now developing slowly. 

 When we consider the rarity of muscular fibres in human 

 skin tissues in comparison with those of animals, their 

 greater frequency in the scrotum and perinaeum suggests 



