408 GENERATION. 



the stomach ; and, between the pharynx and the stomach, there 

 is at first no channel of communication. The anterior por- 

 tion of the pharynx presents, during the sixth week, a large 

 opening, which is afterward partially closed in the formation 

 of the face. The rest of this cavity remains closed until 

 a communication is effected with the oesophagus. The 

 oesophagus appears in the form of a tube, which finally 

 opens into the pharynx above and the stomach below. At 

 this time, there is really no thoracic cavity, the upper part 

 of the stomach is very near the pharynx, the- oesophagus is 

 short, the rudimentary lungs appear by its sides, and the heart 

 lies just in front. As the thorax is developed, however, the 

 oesophagus becomes longer, the lungs increase in size, and 

 finally the diaphragm shuts off this cavity from the cavity of 

 the abdomen. The growth of the diaphragm is from its 

 periphery to the central portion, which gives passage to the 

 vessels and the oesophagus. Sometimes, when this closure is 

 incomplete, we have the malformation known as congenital 

 diaphragmatic hernia. 



The development of the anus is sufficiently simple. At 

 first, as we have seen, the intestine terminates below in a 

 blind extremity ; but, at about the seventh week, a longitu- 

 dinal slit appears below the external organs of generation, 

 by which the rectum opens. This is the anus. It is not 

 very unusual to observe an arrest in the development of 

 this opening, the intestine terminating in a blind extremity, 

 a short distance beneath the integument. This constitutes the 

 malformation known as imperf orate anus, a deformity which 

 can usually be relieved, without much difficulty, by a surgical 

 operation, if the distance between the rectum and the skin be 

 not too great. The opening of the anus appears about a 

 week after the opening of the mouth, 1 at or about the seventh 

 week. 



The rudiments of the liver appear very early, and, in- 

 deed, at the end of the first month, this organ' has attained 



' l BURDACH, Traite de physiologic, Paris, 1838, tome iii., pp. 467, 468. 



