356 ANNUAL OF SCIENTIFIC DISCOVERY. 



hand the nail grew 12 millimetres in 108 days ; for the small finger 

 of the left, 9 millimetres in 152 days ; the growth of all the nails of 

 the left hand required 82 days more than for those of the right, and 

 also there were produced in this time 3 millimetres less than on the 

 right hand. 



The growth of the hair is well known to be much accelerated by 

 frequent cutting. It forms more rapidly in the day than at night, and 

 in hot seasons than in cold. But it is difficult to determine the precise 

 rates. The growth of the hair and nails, as well as the epidermis, 

 pertains to the secretions, and not to the organic structure proper ; foi 

 the quantity of each formed corresponds very nearly with that of the 

 peripheric secretions, especially with transpiration, it increasing in the 

 summer, whilst, on the contrary, the growth and nutrition of the body 

 are most rapid in winter, so that the weight of man, as observed by 

 Sanctorius and others, is greatest in winter ; the small growth of the 

 hair during the night accords with the fact of the diminution of all 

 the secretions, as with that of transpiration, the formation of carbonic 

 acid, the urinary, lacteal, and bilary secretions. L'Instilut, No. 846 ; 

 Sillimari's Journal, July. 



HAIR OF DIFFERENT RACES OF MEN. 



MR. P. A. BROWN, of Philadelphia, has communicated to the 

 American Ethnological Society an essay entitled "the classification 

 of mankind by the hair and wool of their heads," with an answer to 

 Dr. Pritchard's assertion that the covering of the head of the negro 

 is hair, properly so termed, and not wool. The author of this paper 

 states that, on microscopic examination, there appear to be three pre- 

 vailing forms of the transverse section of the filament, viz. the cylin- 

 drical, the oval, and eccentrically elliptical. There are also three di- 

 rections in which it pierces the epidermis, and is prolonged to its 

 apex. The straight and lank, the flowing or curled, and the crisped 

 or frizzled, differ respectively as to the angle which the filament forms 

 with the skin on leaving it. While the cylindrical and oval pile has 

 an oblique angle of inclination, the eccentrically elliptical pierces the 

 epidermis at right angles, and lies in the dermis perpendicularly. The 

 hair of the white man is oval ; that of the Choctaw, and some other 

 American Indians, is cylindrical ; that of the negro is eccentrically 

 elliptical or flat. The hair of the white man, besides its cortex and 

 intermediate fibres, has a central canal, which contains the coloring 

 matter when present. The wool of the negro has no central canal, 

 and the coloring matter is diffused when present, either throughout 

 the cortex, or the intermediate fibres. Hair, according to these obser- 

 vations, is more complex than wool. In hair the enveloping scales are 

 comparatively few, with smooth surfaces, rounded at their points, and 

 closely embracing the shaft; in wool, they are numerous, rough, 

 sharp-pointed, and project from the shaft. Hence, the hair of the 

 white man will not felt ; the wool of the negro will. 



