THE SPLEEN. 



563 



whilst the arteries, from the main trunks to the finest ramifications, all 

 possess them. The structure of the sheaths is precisely that of the 

 trabeculce, but muscles are riot always found in the former when they 

 are contained in the latter e. g. in the Ox while in the Pig they are 

 also very distinct in the sheaths. 



The splenic artery, immediately it enters the organ, and all its prin- 

 cipal branches, divide and spread out into a great number of ramifica- 

 tions, the larger of which proceed towards the anterior margin of the 

 organ, the smaller towards the posterior, forming no anastomoses with 

 those of other principal branches. When they have diminished to the 

 diameter of 1-5-1-10 of a line, they separate from the veins, which till 

 then had run in the same sheath with them, and become connected by 



branches of 0-01-0-02 of a line, with the Malpighian corpuscles in the 

 manner which has been described above ; perhaps, also, sending fine 

 branches into their interior (see 167). Then, often closely applied to 

 the surface of the corpuscles, but, so far as I can observe, not passing 

 through them, as Job. Muller formerly supposed, they enter the red 

 pulp and immediately break up into elegant bundles of minute arteries, 

 the so-called penicilli (Fig. 232), which finally subdivide into true capil- 

 laries of 0-003-0-005 of a line, which throughout the pulp, round the 

 Malpighian corpuscles, as well as elsewhere, unite into a somewhat wider 

 network. 



With respect to the veins, I must especially express myself against 



FIG. 232. An artery with its penicillate ends, from the spleen of the Pig, magnified 25 

 diameters. 



