and their Relation to the Peritoneum. 



481 



It has been previously stated that from its earliest appearance the 

 liver derives a portion of its blood supply from the vessels of that 

 part of the alimentary tract from which it grew ; and the mesentery 

 was stated to be the route by which it arrives at its destination. 

 Now it is clear that, as development progressed, this supply, besides 

 passing through the mesentery, would have to extend through the 

 constriction which forms between the liver and intestine. In the 

 human subject the duodeuum represents that part of the alimentary 

 tract which gives origin to the liver; and, therefore, it seems reason- 

 able to search in its neighbourhood for a vessel which fulfils the con- 

 ditions which have been laid down. The hepatic artery leaves 

 nothing to be desired ; arising behind the peritoneum it runs to the 

 duodenum, and distributes branches to the stomach and intestine ; 

 thence it passes onwards through the lesser omentum to the liver, and 

 it is hardly necessary to remark that the lesser omentum corresponds 

 to the constriction which has just been spoken of. One point with 

 regard to the anatomy of the hepatic artery seems to call for explana- 

 tion and comment ; its passage through the mesentery. In the adult the 

 mesoduodenum is often of insignificant size, so that it is not easy to 

 demonstrate the artery passing through it. At about the middle of 

 intrauterine life the mesoduodenum is long, and no such difficulty 

 exists. Perhaps this observation is strengthened by an examination 

 of the course of the vessel in the shrew. In this animal the whole 

 alimentary tract retains the mesentery, and I have satisfied myself 

 that the hepatic artery passes through it before reaching the liver. 



If it is true that the hepatic artery is the representative of one of 

 the original vessels of the mesentery, many of its peculiarities may be 

 explained. Instead of one the liver may have two or even three 

 arteries (Cruveilhier, " Traite d'Anatomie Descriptive," vol. iii, 

 p. 67). When this is the case the additional vessels may arise from 

 the aorta and reach the liver in the usual way, or they may take 

 origin from the gastric or superior mesenteric arteries ; both of which, 

 it is significant to remark, formerly belonged to the mid-gut. 

 Evidently the organ may appropriate more than one of the original 

 vessels of the mesentery. 



That the hepatic artery should distribute branches to the stomach 

 and duodenum need not excite surprise ; before the appearance of 

 the liver it performed no other function than to supply that part of 

 the intestine which afterwards becomes converted into those oro-ans. 



o 



So far, in order not to introduce needless complications, no 

 reference has been made to the aperture which is called the Foramen 

 of Winslow. The development of the hepatic artery is a factor, but 

 not an essential factor, in its formation. To explain the origin of the 

 Foramen of Winslow, the changes of position which the liver, 

 stomach, and lesser omentum undergo, require to be considered. In 



