208 THE SPLEEN. 



CHAPTER X. 



THE SPLEEN. 



THE spleen is an exceedingly vascular organ, situated in the 

 vicinity of the great pouch of the stomach and supplied abund- 

 antly by branches of the coeliac axis. Its veins, like those of the 

 digestive abdominal organs, form a part of the great portal system, 

 and conduct the blood which has passed through it to the liver, 

 before it mingles again with the general current of the circulation. 



The spleen is covered on its exterior by an investing membrane 

 or capsule, which forms a protective sac, containing the soft pulp 

 of which the greater part of the organ is composed. This capsule, 

 in the spleen of the ox, is thick, whitish, and opaque, and is com- 

 posed to a great extent of yellow elastic tissue. It accordingly 

 possesses, in a high degree, the physical property of elasticity, and 

 may be widely stretched without laceration ; returning readily to 

 its original size as soon as the extending force is relaxed. 



In the carnivorous animals, on the other hand, the capsule of 

 the spleen is thinner, and more colorless and transparent. It con- 

 tains here but very little elastic tissue, being composed mostly of 

 smooth, involuntary muscular fibres, connected in layers by a little 

 intervening areolar tissue. In the herbivorous animals, accordingly, 

 the capsule of the spleen is simply elastic, while in the carnivora it 

 is contractile. 



In both instances, however, the elastic and contractile properties 

 of the capsule subserve a nearly similar purpose. There is every 

 reason to believe that the spleen is subject to occasional and per- 

 haps regular variations in size, owing to the varying condition of 

 the abdominal circulation. Dr. William Dobson 1 found that the 

 size of the organ increased, from the third hour after feeding up to 

 the fifth ; when it arrived at its maximum, gradually decreasing 

 after that period. When these periodical congestions take place, 



1 In Gray, on the Structure and Uses of the Spleen. London, 1854, p. 40. 



