OF THE HUMAN SKIN. 63 



qiient scratching not only disagreeable, liiit pos- 

 itively injurious. The effect of the parasites in 

 the shaft of the hair and the hair-follicles is much 

 more deleterious, so far as the life and growth of 

 the hairs are concerned ; for these latter may in 

 consequence either drop out entirely, or become 

 brittle, dry, and easily broken and rubbed off, 

 those remaininsr beins; lis^hter in color, and not 

 so strons: and^ healthy. Absolute loss of hair 

 from the whole surface of the cutaneous envelope 

 may be caused by vegetable parasites, or the en- 

 tire scalp rendered as smooth and free of them as 

 a billiard-ball. Of course this must not be con- 

 founded with baldness, the result of natural or 

 premature loss of the hair. Further than this, 

 the presence of vegetable growth in the epidermis 

 or hair-follicle produces an eruption of a peculiar 

 character, simulating some natural cutaneous dis- 

 eases, and causing, also, itching and consequent 

 scratching. The nails, when infested, become 

 brittle, dry, thickened, and crumbling. More- 

 over, masses of vegetable growth may lie half 

 imbedded in the skin, which, producing loss of 

 the hair, and being of a yellowish color, finally 

 'give the cutaneous surface a most revolting appear- 



