102 IMMUNITY IN HEALTH 



That the subepithehal lymphatic glands are a risk to 

 their owners from the effects of acute attacks of in- 

 flammation can hardly be doubted. If their possession 

 involved no counterbalancing benefits, all variations in 

 the direction of their suppression would have a strong 

 bias in their favour in the struggle for existence and 

 these organs would tend to disappear in the race. In 

 the words of Professor Keith (1912), '' We know from 

 their fossil remains that the great anthropoids are of 

 extreme geological antiquity. Were their appendices 

 (identical in structure with the human appendix) in- 

 jurious or vestigial structures there has been ample 

 time to accomplish their complete suppression." 



Moreover, any organ that ceases to be of value de- 

 generates. This principle of degeneration is perhaps 

 imperfectly realised. 



It has probably nothing to do with disuse. " Disuse 

 Inheritance " has long been abandoned as an untenable 

 view. 



Nevertheless, an organ, the lack of utility of which 

 removes it from the sphere of natural selection, be- 

 comes the sport of variation and chance. Its constancy 

 diminishes with every variation which arises, and the 

 accurate inter-relationship of its parts falls in the 

 average member of ensuing generations. So it is that 

 the eyes of species that have lived for countless gener- 

 ations in the dark have ceased to see. 



