388 INTERNAL SECRETIONS OP PANCREAS AND SPLEEN. 



late the functional mechanism of the spleen to that of other 

 organs reviewed were it not that dilation of the latter can also 

 be produced by stimulating other nerves. Indeed, Howell 

 says: "The spleen is richly supplied with nerve-fibers which, 

 when stimulated either directly or reflexly, cause the organ 

 to diminish in volume. According to Schafer, 14 these fibers 

 are contained in the splanchnic nerves, which carry also inhib- 

 itory fibers, whose stimulation produces a dilation of the spleen." 

 We have not so far found the need of such structures as 

 "inhibitory nerves," and it would seem as if this term were 

 applied, in this instance, to the fibers to which we have as- 

 cribed the mission of contracting the arterioles that govern 

 the intrinsic blood-supply of an organ. Especially does this 

 appear to be the case since these inhibitory fibers are described 

 as originating from the splanchnic: i.e., the sympathetic sys- 

 tem. The latter, if considered as forming part of the general 

 motor system, would precisely coincide with the origin of the 

 nerves which have appeared to us to cause contraction of these 

 small vessels and thus produce secondary dilation of the capil- 

 laries incident upon functional activity. 



. The interpretation of the splenic functional mechanism 

 in accordance with our views is greatly facilitated when the 

 microscopical anatomy of the organ is considered in the light 

 of F. P. Mall's 15 researches. The organ is divided, as is the 

 liver, into lobules, each of which is bounded by "interlobular" 

 trabeculas: those to which we have already referred. Each 

 lobule is about 1 millimeter in diameter, is partitioned into 

 about ten compartments by intralobular trabeculae, and receives 

 an artery which sends minute branches to each compartment. 

 There is also considerable analogy between each one of these 

 compartments and the hepatic lobule, the hepatic cells being 

 represented by masses of pulp, separated by venules, which 

 vessels carry back to the veins leading to the greater splenic 

 vein the various elements transferred to the liver. The pulp 

 itself is made up of an extremely delicate reticulum, in which 

 are found red corpuscles, lymphocytes, remains of corpuscles 



"Schafer: "Proceedings of Royal Society," London, 1896, vol. lix, No. 365; 

 and Journal of Physiology, 1896, vol. xx. 



F. P. Mall: Johns Hopkins Hospital Bulletin, Sept., Oct., 1898. 



