OF THE SKIN. 151 



nearly full-grown foetus, 47*5 per cent, of ethereal extract, 150 

 of alcoholic extract, 3'3 of watery extract, 40 of acetic acid ex- 

 tract (earthy phosphates and albuminous substances), epidermis 

 and lanugo 23-7. In the ethereal extract the reaction of bilin 

 was absent and the fresh vernix contained a large quantity of 

 water, which in all probability had entered its cells from the 

 liquor amnii. The smegma generally appears about the sixth 

 month, varies greatly in quantity, and is, especially in newly- 

 born infants, sometimes very greatly developed (as much as 

 3i drachms, Buek), sometimes wholly wanting; in which 

 latter case it either becomes mixed with the liquor amnii, 

 which in fact often contains epidermic cells as well as fat (Mark, 

 in Heller's 'Archiv/ 1845, p. 218), or may have been from the 

 first, less developed. After birth the smegma is thrown off in 

 the course of from two to three days, and the permanent epi- 

 dermis appears, of whose further changes up to the adult state 

 there is little to be said. In a child four months old the 

 epidermis measured — 



Epidermis in toto. Rete Malp. Horny layer. 



On the heel 0-26'" 0-12'" 0-14'" 



On the back of the foot . . 0-048— 0-06'" 0-032— 004'" 0-016—0-02'" 



On the palm 0-07— 0-1'" 004—007'" 003" 



On the back of the fingers . 0-036— 0-07'" 0-04— 005'" 0-016—0-02'" 



On comparing this with the adult, it is to be observed that the 

 epidermis of the young child is disproportionately thick, and 

 that this thickness depends especially upon the rete Malpighii, 

 whilst the horny layer exhibits only a slight development. The 

 pigment of the rete Malpighii arises, in the coloured races, only 

 after birth. P. Camper (' Kleinere Schriften/ 1782, Bd. I, 

 p. 24) saw a negro child, which at its birth was reddish, and 

 hardly differed from that of an European, rapidly become tinged 

 black at the edges of the nails and round the nipple. On the 

 third day the genitalia became coloured, and on the fifth and 

 sixth the blackness spread over the whole body. In Europeans 

 also, at birth, the pigment of the areola and of the other places 

 which have been mentioned is not yet present : it is gradually 

 developed in the course of the first year, so that in children 

 of two or three months old it is only indicated. 



In investigating the skin, perpendicular and horizontal sec- 

 tions of fresh, dried, and boiled preparations are serviceable : 



