332 PHILOSOPHY OF ZOOLOGY. 



found pate and inert. These facts seem to warrant the 

 conclusion, that the spleen is subservient to the functions of 

 the liver, and probably supplies the deficiency of fluid which 

 the branches of the vena portarum are unable to obtain 

 from the abdominal viscera. 



Sir EVERAUD HOME at one time considered the spleen as 

 the medium by which fluids, unnecessary for the process of 

 digestion, were conveyed from the cardiac portion of the 

 stomach, into the system, or into the urine to be excreted. 

 But, in subsequent experiments which he performed, co- 

 loured fluids injected into the stomach, reached the urine, 

 even when the spleen had been previously extirpated, and 

 even after a ligature prevented the contents of the thoracic 

 duct from being poured into the circulating system. Al- 

 though he adopted this opinion hastily, with a praiseworthy 

 candour he frankly published the demonstration of his er- 

 ror *. I have said hastily, because the well known circum- 

 stances of quadrupeds which do not drink, possessing a 

 spleen equal in size to those which swallow large quantities 

 of fluid, and the attachment of this organ to the first sto- 

 mach of ruminating quadrupeds, into which the drink does 

 not enter, furnished objections of great weight. 



The next organ in connection with the digestive system, 

 is the Peritoneum. This membrane lines the walls of the 

 abdomen, and insinuates itself among the intestines, form- 

 ing various duplicatures, distinguished by appropriate 

 names. It is composed of cellular tissue, and contains nu- 

 merous bloodvessels and absorbents. Its free surface is 

 kept constantly moist by an aqueous exhalation. It varies 

 in thickness and tenacity in different animals ; and although 

 transparent or whitish among quadrupeds and birds, is found 

 variously coloured in reptiles and fishes. Its obvious use 

 is to protect the intestines from rubbing against one an- 



* HOME'S Lect. on Comp. Anat. vol. i. p. 221, 245. 



