508 THE HUMAN EMBRYO. 



round. The hairs are plentiful, and about 5 or 6 mm. in 

 length. 



The several bones forming the roof of the skull become 

 strongly convex, the central portion of each, from which ossifica- 

 tion starts, forming a very evident prominence. The eyelids, 

 which have been closed since reaching their fall size in the fourth 

 month, now open. 



The whole of the large intestine is filled with a dark olive- 

 green viscous meconium. The liver is still very large relatively 

 to the whole body, and is of a deep brownish red colour. 



The testes have, as a rule, descended as far as the inguinal 

 rings, and may even have entered the inguinal canals. 



The end of the seventh month is of interest, as being perhaps 

 the earliest period at which the foetus can be born with any 

 reasonable chance of surviving. 



13. The Eighth Month. 



During the eighth month the increase in bulk is more 

 marked than that in length. At the end of the month the 

 total length of the foetus, from the head to the coccyx, is about 

 28 cm. ; and from the head to the heels about 40 cm. The 

 weight varies from 2 to 2J kilogrammes. 



The skin is of a brighter flesh colour than before, and is 

 covered all over with the sebaceous deposit known as c vernix 

 caseosa.' This substance, which usually makes its appearance 

 about the middle of gestation, was formerly considered to be a 

 deposit formed from the liquor amnii, but appears rather to 

 consist of matter formed by the cutaneous glands of the foetus, 

 mixed with dead epithelial cells. It varies much in quantity 

 in different cases, and is always more abundant in certain situa- 

 tions, notably the head, axillas, and groins. 



The chin is now far more prominent than before, the lower 

 jaw equalling the upper in length. One of the testes, usually 

 the left one, has passed through the inguinal canal into the 

 scrotum, while the other is, as a rule, still in the canal. There is 

 no ossification in the lower epiphysis of the femur. 



14. The Ninth Month. 



At the full time the foetus measures about 35 cm. from the 

 head to the coccyx, and 50 cm. from the head to the heels. 

 The weight is, on the average, from 3 to 3J kilogrammes. 



