EPIDERMAL GROWTH. 19 



external objects, as we may see in the flaking off and wear- 

 ing down of the hoofs of an unshod horse. The exfoliation 

 of hair is accomplished naturally by the shedding of the 

 scales which cover the hairs, as we may observe by the 

 thinned-out condition of their ends. The exfoliation of 

 epidermis is hastened by the action of perspiration. Thus, 

 cuticle can be far more easily rubbed off the skin of a man 

 who is sweating freely, than off that of a man whose body is 

 cool. Also, vigorous grooming tends to make the coat both 

 fine and short. Contrary to the general opinion that brush- 

 ing stimulates the growth of hair, we have the fact that the 

 Sikhs, who have longer hair than any other people in the 

 world, keep their hair as a rule closely coiled up on their 

 heads, and undo it, for purposes of cleaning, only after long 

 intervals of time. I may explain that their religion forbids 

 them to cut their hair. When stationed in the Punjab, which 

 is the country of the Sikhs, I have seen many of them making 

 their, probably, annual capillary toilette, and have often 

 noticed among them, instances of the hair reaching to the 

 ground, while the owners were standing upright. In fact, it 

 is no uncommon occurrence to find Sikhs with hair 6 ft. long ! 

 I think we may safely attribute the extraordinary length of 

 their hair to comparative absence of friction, and to the pro- 

 tection against the action of perspiration afforded by the 

 compact condition which the hair is made to assume on the 

 head. 



The horns of animals which wear this kind of epidermal 

 growth, are almost always more massive in cold countries 

 than in hot ones, among members of the same species, as we 

 see in reindeer, ovis ammon, and ibex. Also, observations 

 in the respective countries will show us, that the hoofs of 

 Tibet and Finnish ponies are thicker than those of Indian 

 horses. We must here bear in mind that the colder a 

 climate, the dryer it is, other things being equal. 



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