360 FISHES. 



The intei'vals are occupied by the spleen, (//) ; this is placed in the 

 first fold by the ovary (^), which is often veiy voluminous ; and by 

 the vessels, and lastly, much of the fat poured out by a cellular tissue, 

 produced by the peritoneal envelope, and which represents in some 

 respects the omenta of mammalia. 



This intestine decreases slightly in its diameter, as far as the middle 

 of its last line, where a very perceptible swelling marks (L), the com- 

 mencement of the large intestine or rather the rectum. There is 

 also, internally, in this place a cii'cular small valve, formed by a very 

 slight fold of the internal membrane, which prevents the matter that 

 have once descended in the rectum from getting back again. 



The spleen in fishes (//), is variable in position, A'olume and size, 

 but it is always present and as invariably solitary ; most frequently 

 it is near the middle of the folds of the intestinal canal. It only receives, 

 as in the superior animals, arterial blood Avhich it elaborates and 

 transmits to the liver, where it sends also the blood of nearly the 

 whole of the remainder Of the intestine ; its relative positions with the 

 stomach differ very considerably, and very often too, from Avhat we 

 see in the mammalia, and we cannot attribute to it any function 

 which would constantly arise from the greater or less extent of the 

 pressure of the stomach upon it. 



The liver (M), is generally large, and is situated more towards 

 the left than the right ; its figure and the number of its lobes are very 

 various, and this number is sometimes even excessive ; but it is 

 always furnished with a gall bladder (A'), which is sometimes mode- 

 rate in size, sometimes very long, and suspended at some distance 

 from the liver. The excretory canal («), is inserted in some high 

 point in the intestine, and sometimes even in the stomach. The latter 

 I have seen in the moon-fish. The hepatic canals (w), are sometimes 

 very numerous, and they are joined successively to the cystic canal. 



The substance of the liver is softer than it is in many quadrupeds 

 and birds, and its tissure is almost always penetrated with a copious 

 oily substance. 



The mesentery of fishes is altogether imperfect, and is frequently 

 reduced to mere bands surrounding the vessels and nerves and con- 

 necting the peritoneum, with the peritoneal coat of the canal. 



It is very common for this tunic to be prolonged in appendages 

 filled with oleaginous grease, and Avhich are really nothing but 

 omenta, (P, P). 



In the mesentery we can never find conglobate glands, and it has 

 always its lacteals as other animals. 



Indeed, the absorbent system in fishes does not appear to be less 

 than in the other vertebrated animals*, and it is certain at all events, 

 that those of the intestinal canal are uncommonly numerovis, and 



* William Hewson and Alexander Munro have had a contest respecting the prior- 

 ity of the discovery of lymphatic vessels in the oviparous vertebrated animals. 

 Mnnro is positive that he has seen them in birds in 1 758, 1 759, and 1 760, and men- 

 tioned them in 1767 ; also that he discovered them in the ray, 1760 : and in the tor- 

 toise in 1765 ; this was published in 1770. Hewson's Memoir on the lymphatics of 

 birds in Philosophical Transactions was 1768, and on two of the reptiles in 1769. 



