166 DARWINISM TO-DAY. 



animals when pursued by an enemy, or slight differences 

 in the length of neck of the giraffe in time of scarcity of 

 foliage, or slight differences in the effectiveness of the 

 organs of sense at times of approaching danger, or in 

 endurance of cold, heat, hunger, dryness, etc., or in 

 the clothing of hairs or feathers, the number of capil- 

 laries in the skin, or richness of glandular secretion, and 

 the like, in times of special stress of weather. "Dodel- 

 Port 3 has shown that microscopically fine hairs are capable 

 of keeping plant-lice away from leaves or buds, and that 

 very slight differences in the specific gravity of the seeds 

 of water-plants may determine whether these seeds sink to 

 the bottom and consequently germinate or not. For the long 

 flights of migratory birds or for birds like our house-doves 

 which protect themselves from birds of prey by swift flights 

 upward to great heights, every smallest amount of advan- 

 tage in the pneumaticity of the bones will be of worth and 

 finally of vital advantage, just as every racing bicyclist 

 knows by experience that for his record-breaking at- 

 tempts he must have a machine in which every part is 

 made as light as possible, for the effects of weight are cumu- 

 lative in course of time." And Plate fills a couple of pages 

 with other similar cases. "Whoever scrutinises the life of 

 nature and of man with biologically trained eye sees over 

 and over again the coming of great effects from slight 

 causes. The average of accidents in factories increases in 

 proportion to the age of the workers, because muscular 

 strength and keenness of the sense organs decrease with 

 increasing age. In each age-class the difference is but 

 slight, but in spite of that it demands its sacrifice. Nageli, 

 in a paper concerning the abundance of tuberculosis, showed 

 that among 500 dead human bodies examined 97 per cent, 

 showed traces, at least, of tuberculosis. That is, practically 

 every adult human is tainted by this disease. Now how 

 often must slight differences in body structure, life habits, 



