156 SPECIAL HISTOLOGY. 



except that by maceration, &c., it is much more easily separated from 

 the corium than in the adult. The non-nucleated horny plates measured 

 0-012--016, on the labia minora, where they possess nuclei 0-016-0-02 

 of a line. 



During embryonic life a desquamation of the epidermis occurs, which 

 is perhaps repeated several times. Such is the fate, probably, of the 

 layer of polygonal cells which arises first of all, and which in the second 

 to the fourth months, becomes metamorphosed into an almost structure- 

 less membrane, and is then no longer to be found; perhaps also of the 

 layer of epidermis, which covers the points of the hairs which have not 

 yet appeared externally (vide infra Hairs); and in the second half of 

 the foetal period it may be easily demonstrated as an actively occurring 

 process. From the fifth month onwards, in fact, continually increasing 

 desquamation of the external epidermic cells takes place, and these 

 becoming in most parts mixed up with the sebaceous secretion of the 

 skin, form the so-called vernix caseosa or smegma embryonum. This is 

 a whitish or yellowish, viscid, inodorous material, which, especially from 

 the sixth month onwards, covers the whole surface of the foetus with an 

 often considerably thick and even laminated substance, which is most 

 abundant upon the genitalia, on the flexor side of the joints (axilla, 

 knee, nates), on the sole, the palm, the back, the ear, and on the head 

 in large quantity, and when microscopically examined consists mainly 

 of epidermic cells, but also contains sebaceous cells and fat globules. 

 According to Davy ("Lond. Med. Gaz.," March, 1844) the vernix 

 caseosa contains in 100 parts, 5*75 elain, 3*13 margarin (8*88 fat) ; the 

 rest, 91*12 per cent., must be reckoned as epidermic scales, for since 

 the vernix caseosa contains no free fluid, the 77 '87 per cent, water and 

 13-25 solid substance found by Davy must be laid to the account of 

 epidermic cells. This also holds good of Buck's analysis (" De Vernice 

 caseosa," Halis, 1844) who found in 100 parts, 10-15 fat, 5-40 epithe- 

 lium, and 84-45 water (so that there was 89-85 of epithelium) ; and also 

 in two other cases, in which the water was not exactly determined, he 

 found 14-80 and 9-31 per cent, of fat, and therefore 86-20 to 89-69 of 

 moist epithelium. According to Buek, the fat of the vernix caseosa 

 contains no cholesterin, as had been stated by Fromherz and Gugert, 

 but oleic acid, and either ^tearic or margaric acid, which are probably 

 not free, but combined with glycerine, a circumstance which also 

 evidences its origin from the sebaceous glands, in which, normally, no 

 cholesterin is formed. Lehmann found (1. c.) in the dry vernix caseosa 

 of a nearly full-grown foetus, 47*5 per cent, of ethereal extract, 15*0 of 

 alcoholic extract, 3-3 of watery extract, 4*0 of acetic acid extract (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 



