THE FCETUS. 199 



we should attempt to straighten it out for the purpose of measuring 

 the distance from the vertex to the os coccygis, the front of the neck 

 and the abdomen would rarely fail to be lacerated; at two months 

 the firmness of the parts mostly enables us to avoid such an accident, 

 but as the foetus may be either more or less straight, there will arise 

 numerous discrepancies in the results. The habitually flexed state 

 of the lower extremities renders it too difficult to extend them so as 

 to comprise their length in a rigorous admeasurement of the embryo. 

 Authors not having informed us which of these methods they 

 adopted, it is useless to look further for the reasons of the discre- 

 pancy observable in their accounts of this subject. It is true that 

 the most minute precautions will not permit us to specify within one 

 line, the length of a foBtus more than a month old; but happily, such 

 a degree of precision can be a matter of small moment in the eyes 

 of the observer. In the present instance, the measurements that I 

 shall point out must in general be understood, as applying to the 

 foetus in its naturally curved position, that is, the space extending 

 from the occifiut to the coccyx; and I believe this diameter never 

 exceeds eighteen or twenty lines before the end of the second month. 



508. The skin of the human embryo has no real existence until 

 at a pretty advanced period of its growth, while the sort of circle 

 which it at first constitutes, is nothing more than a homogeneous 

 gelatinous substance of slight consistency; the epidermis cannot be 

 distinguished from the skin until after the second month. 



509. At three months the teguments are distinct, but still gelati- 

 nous and of a rose color. The eye-lids and mouth remain shut, 

 the nose is very projecting, the head very large; the costal arches 

 and bones of the fore-arm are visible through the transparent sub- 

 stances in which they are enclosed. The fingers and toes are per- 

 fectly distinct, and covered on the dorsal surface of their extremities 

 with a reddish plate which possesses the shape of the nail; from the 

 vertex to the coccyx the fostus is three inches in length. 



510. At four months the skin is much firmer, and at certain 

 points is furnished with adipose granulations. The head begins to 

 be covered with down; the scrotum, or the greater and lesser labia 

 are formed; the anus is open; and if in the measurement we comprise 

 the lower extremities, which, notwithstanding the common opinion 

 to the contrary, are as long as the thoracic members, the foetus 

 will be from five to six inches in length. 



511. At Jive months a little down and some particles of seba- 

 ceous matter are observable upon various portions of the skin; the 

 hairs begin to grow, but are still white, or without any determinate 

 color. The teguments are less transparent, although still of a rose 



