DIGESTIVE SYSTEM. 



or less intimately connected with the digestive organs. The 

 first of these is the 



Spleen. This organ is confined to the vertebral animals. 

 In general it is single. In a few species, however, it is di- 

 vided into several lobes. Its texture is vascular, consisting 

 of a great assemblage of bloodvessels, united by a small 

 quantity of cellular substance. It is covered externally by 

 the peritoneum, beneath which there is another integument 

 peculiar to it, which penetrates its substance along with the 

 vessels. The arteries by which the spleen is supplied with 

 blood, are, in general, branches from those of the stomach ; 

 and the veins in which these terminate, ultimately pour 

 their contents into the liver. In position, the spleen is, in 

 some cases, connected with the stomach ; in others, more 

 intimately related to the liver, but united to both by means 

 of its bloodvessels. 



The use of this organ in the animal economy remains to 

 be ascertained. Though largely supplied with bloodvessels, 

 it has no excretory duct, nor is its vascular, rather than 

 glandular structure, favourable to the supposition that it is 

 a secreting organ. Its lymphatic vessels are regarded by 

 some as " nowise remarkable for their number or size*; 1 ' 

 while others assert, that they " are both larger and more 

 numerous than in any other organ )*." 



It seems to be generally admitted, that the blood of the 

 splenic vein is more fluid, and coagulates with greater diffi- 

 culty than the blood in the splenic artery. Therefore, 

 some change must have taken place on the blood in the 

 spleen. By this change, the blood is probably prepared 

 for the use of the liver, to which it flows. When the spleen 

 has been removed from a dog, the cystic bile has been 



MONRO on Fishes, p. 37. 



f HOME'S Lect. on Comp. Anat. vol. i. p. 235. 



