5 1 6 SPLEEN. [CHAP. xxxv. 



and, as it enters into the organ, receives an investment of fibrous 

 tissue, which is prolonged upon the branches, forming their 

 sheaths, which are connected with the trabeculse. 



Lymphatics. But little is known of the ultimate arrangement 

 of the lymphatics of the spleen, or of the manner in which they 

 commence. They are certainly not connected with the Malpighian 

 corpuscles, nor can we look upon them as the channels which 

 carry off the secretion of the organ, a view which has been advo- 

 cated by many observers. 



Nerves. The nerves of the spleen are derived from the splenic 

 plexus formed by branches from the left semilunar ganglion, and 

 from the right pneumo-gastric nerve. The branches are distributed 

 to the coats of the arteries ; they may be traced upon them for a 

 considerable distance, but gradually they become lost. 



Changes in the Blood in the Spleen. The most important peculi- 

 arities in splenic blood appear to be the following : The total 

 quantity of solid matter is considerably less in the blood of the 

 splenic vein than in arterial or venous blood, and the blood cor- 

 puscles are reduced to half the quantity. The greatest reduction 

 seems to occur at the period of the greatest turgescence of the 

 spleen. Mr. Gray has made the very interesting observation, that 

 in starved animals no change is observable. The albumen is in- 

 creased, particularly when the amount of blood corpuscles is much 

 diminished. The quantity of fibrine in splenic blood, is also found 

 to be increased. The serum is often observed of a pale reddish 

 brown colour. 



Uses of the Spleen. We have now to consider the uses of the 

 spleen in the animal economy. From the large quantity of elastic 

 tissue in its capsule and trabeculse, it seems eminently adapted to 

 undergo great changes in volume ; and the direct experiments of 

 Dobson, and many other observers, have proved that it becomes 

 much enlarged during digestion, as well as when blood was injected 

 into the jugular vein. Connected with the large veins of the portal 

 system, it forms a dilatable diverticulum, or reservoir, in which 

 blood may, for a certain time, be contained, thus preventing dan- 

 gerous congestion of the veins of the liver, and some other abdo- 

 minal viscera, and indeed, of the venous system generally. The 

 spleen does not appear to be contractile. In several careful ex- 

 periments, Mr. Gray was never able to cause more than a slight 

 corrugation of the suiface of the organ by the galvanic current, 

 although active contractions could be produced in the oesophagus, 

 or stomach, under similar circumstances. In no instance out of 



