SEBACEOUS MATTER. 325 



quently in the contents of sebaceous cysts, does not exist in the normal se- 

 cretion. 



During the later months of pregnancy and during lactation, the sebaceous 

 glands of the areola of the nipple become considerably distended with a 

 grayish -white, opaque secretion, containing oily globules and granules. Fre- 

 quently the fluid contains also a large number of epithelial cells. During the 

 periods above indicated, the secretion here is always much more abundant 

 than in the ordinary sebaceous glands. 



Smegma of the Prepuce and of the Ldbia Minora. In the folds of the 

 prepuce of the male and on the inner surface and folds of the labia minora 

 in the female, a small quantity of a whitish, grumous matter, of a cheesy 

 consistence, is sometimes found, particularly when proper attention is not 

 paid to cleanliness. The matter which thus collects in the folds of the pre- 

 puce has really little analogy with the ordinary sebaceous secretion. Exami- 

 nation with the microscope shows that it is composed almost entirely of 

 irregular scales of epithelium, which do not present the fatty granules and 

 globules usually observed in the cells derived from the> sebaceous glands. 

 The production of this substance is probably independent of the secretion of 

 sebaceous matter, as it is formed chiefly in parts of the prepuce in which the 

 sebaceous glands are wanting. 



The smegma of the labia minora is of the same character as the smegma 

 preputiale ; but it contains drops of oil and the other products of the seba- 

 ceous glands found in these parts. 



Vernix Caseosa. The surface of the foetus at birth and near the end of 

 utero-gestation is generally covered with a whitish coating, or smegma, called 

 the vernix caseosa. This is most abundant in the folds of the skin ; but it 

 usually covers the entire surface with a coating of greater or less thickness 

 and of about the consistence of lard. There are great differences in foetuses 

 at term as regards the quantity of the vernix caseosa, In some the coating 

 is so slight that it is observed only on close inspection. There are few analy- 

 ses which give accurately the chemical composition of this substance ; and 

 the best idea of its constitution and mode of formation can be formed from 

 microscopical examinations. If a small quantity be scraped from the surface 

 and be spread out upon a glass slide with a little glycerine and water, it will 

 be found on microscopical examination, to consist of a large number of epi- 

 thelial cells with a very few small, fatty granules. These cells, after desicca- 

 tion, constitute about ten per cent, of the entire mass. The fatty granula- 

 tions are very few and do not seem to be necessary constituents of the vernix, 

 as they are of the sebaceous matter. In fact, the vernix caseosa must be re- 

 garded as the residue of the secretion of the sebaceous glands, rather than 

 an accumulation of true sebaceous matter. 



The office of the vernix caseosa is undoubtedly protective. In making a 

 microscopical preparation of the cells with water, it becomes evident that 

 the coating is penetrated by the liquid with very great difficulty, even when 

 mixed with it as thoroughly as possible. The protecting coat of vernix cas- 

 eosa allows the skin to perform its office in utero, and at birth, when this 



