886 THE SPLEEN". 



cat, and to a smaller extent in that of the ox and sheep, there has been 

 found an abundant admixture of plain muscular fibres, resembling those of 

 the middle coat of arteries. Meissner and W. Miiller affirm that they also 

 find muscular fibres in the trabeculse and fibrous coat of the human spleen ; 

 but the existence of such fibres is denied by other observers. The elasticity 

 of the fibrous coat and trabeculae, together with whatever amount of mus- 

 cularity they may possess, renders the spleen capable of the great and 

 sudden alterations in size to which it is subject. 



The pulp of the spleen is of a dark reddish-brown colour : when pressed 

 out from between the trabeculse it resembles grumous blood, and, like that 

 fluid, it acquires a brighter hue on exposure to the air. This pulpy eub- 

 stance lies altogether outside the veins, between the branches of the venous 

 plexus. As shown by the microscope, it consists chiefly of numerous 

 rounded granular bodies, which have a reddish colour, and are about the 

 size of the blood corpuscles. Their cohesion is very slight, and the termi- 

 nal tufts of the arterial system of vessels are spread out amongst them. In 

 examining the substance of the spleen, elongated caudate corpuscles are 

 seen in rather large numbers. And besides these there are round nucleated 

 cells, and free nuclei. There are also large cells, some of which are nucle- 

 ated, and others not, but both of which contain blood-corpuscles in various 

 states of change. 



The splenic artery and vein, alike remarkable for their great proportionate 

 size, having entered the spleen by six or more branches, ramify in its inte- 

 rior, enclosed within the elastic sheaths already described. The smaller 

 branches of the arteries run along the trabeculse, and terminate in the 

 proper substance of the spleen in small tufts of capillary vessels arranged 

 in pencils. These are supported by fine microscopic trabeculse which run 

 through the pulp in all directions. The main branches of artery which 

 enter the spleen appear to have few or no anastomoses within the substance 

 of the organ, for it has been justly remarked that, if one of them be 

 injected, the material of injection will return by the corresponding vein 

 before spreading to other parts of the spleen : and it only returns by 

 the vein after injection of the pulp. The veins, which greatly exceed the 

 arteries in size, anastomose frequently together, so as to form a close venous 

 plexus, placed in the intervals between the trabecuJae, and supported by 

 them. There is still great difference of opinion as to the manner in which 



Fig. 621. Fig. 621. A SMALL FRAGMENT OP A PREPARED 



SPLEEN UNRAVELLED (from Kolliker). 5 J 5 



a, finest reticulum ; b, transversely cut 

 capillary veins which have lost their epithelium; 

 C, veins in which the epithelium is more or less 

 preserved ; d, longitudinal section of the same ; 

 e, a capillary vessel lying in the finest splenic 

 tissue, 



the arteries and veins are connected. 

 According to Gray, the capillaries 

 traverse the pulp in all directions, and 

 terminate either directly in the veins, 

 or open into lacunar spaces, from which 

 the veins originate. Billroth and Kolliker admit only the direct termina- 

 tion in veins ; Stieda and W. Miiller maintain that a network of inter- 

 cellular passages intervenes. 



