DISEASES OF THE SPLEEN. 



CHAPTER I. 



HYPERJEMIA OF THE SPLEEN. 



ETIOLOGY. The variations in the amount of blood in an orgaii 

 may be the more decided, the more yielding its parenchyma and en- 

 velope, and the more numerous its vessels, and the thinner their walls. 

 The spleen has a very yielding capsule, its numerous vessels have very 

 thin walls, and appear to communicate with large cavities within. This 

 explains how the spleen may be enormously distended by injections 

 of water, or by blowing up, as well as the fact that, during life, the 

 amount of blood in it may be very much increased, and it may, conse- 

 quently, be very decidedly enlarged. 



The slighter the elasticity of the envelope, and of the walls of the 

 vessels of an organ, the slower the disappearance of distention induced 

 by any temporary cause. If we imagine an organ where the envelope 

 and the walls of the vessels have no elasticity, it would remain perma- 

 nently enlarged, if once distended by a momentary increase of the 

 blood flowing in, or by a momentary obstruction to that flowing out ; 

 just as a wax-tube, that has a fluid passing through it, remains perma- 

 nently dilated if we momentarily increase the pressure on its inner 

 wall. As the capsule, trabeculae, and walls of the splenic vessels offer 

 but little opposition to its enlargement, so also, from their slight elas- 

 ticity, they can only slowly remove any enlargement of the organ. If 

 the spleen be swollen during a paroxysm of intermittent fever, after 

 the subsidence of the paroxysm, it remains enlarged longer than other 

 organs that were enlarged at the same time, but which were richer in 

 elastic elements, and particularly such as had vessels with more elas- 

 ticity than the vessels and cavities of the spleen. We shall hereafter 

 show that the decrease of swelling of the spleen is probably caused 

 by its contractile elements. 



In the spleen as in other organs we must distinguish two forms of 

 hypencmia, fluxion and obstructive engorgement. 



