BLOODVESSELS, NERVES AND LYMPHATICS OF THE SPLEEN 381 



addition are found red blood-corpuscles, some natural in form and size 

 and others more or less altered, with pigmentary granules, both free 

 and enclosed in cells. 



Bloodvessels, Nerves and Lymphatics of the Spleen. The quantity 

 of blood which the spleen receives is large in proportion to the size of 

 the organ. The splenic artery is the largest branch of the coeliac axis. 

 It is a vessel of considerable length and is remarkable for its tortuous 

 course. It gives off several branches to the adjacent viscera, and as it 

 passes to the hilum, it divides into three or four branches, which again 

 divide so as to form six to ten vessels. These penetrate the substance 

 of the spleen, enveloped in fibrous sheaths with the veins, nerves 

 and lymphatics. In the substance of the spleen the arteries branch 

 rather peculiarly, giving off many small ramifications in their course, 

 usually at right angles to the parent trunk. These are accompanied by 

 the veins until they are reduced to -^ or ^ of an inch (0.32 or 0.42 

 millimeter) in diameter. The two classes of vessels then separate, and 

 the arteries have attached to them the corpuscles of Malpighi. It is 

 also a noticeable fact that the arteries passing in at the hilum have no 

 inosculations with each other in the substance of the spleen, so that the 

 organ is divided up into six to ten vascular compartments. 



The veins join the small branches of the arteries in the spleen-pulp 

 and pass out of the spleen in the same sheath. They anastomose quite 

 freely in their larger as well as their smaller branches. Their calibre 

 is estimated as about twice that of the arteries. The estimates which 

 have put the calibre of the veins at four or five times that of the arteries 

 probably are exaggerated. The number of veins emerging from the 

 spleen is equal to the number of arteries of supply. 



By most anatomists two sets of lymphatic vessels have been recog- 

 nized, the superficial and the deep. The superficial lymphatics are in 

 the investing membrane of the spleen and probably are connected with 

 the deep lymphatics. The origin of the deep vessels is somewhat ob- 

 scure. Lymphatic spaces, with anastomosing venous spaces or sinuses, 

 however, surround the Malpighian bodies and permeate the spleen-pulp. 

 It is probable that lymph and blood are mixed in these sinuses (see 

 Plate IX, Fig. 2). At the hilum the deep lymphatics are joined by 

 vessels from the surface. The vessels, numbering five or six, then 

 pass into small lymphatic glands and empty into the thoracic duct 

 opposite the eleventh or twelfth dorsal vertebra. No lymphatic vessels 

 have been observed going to the spleen. 



The nerves of the spleen are derived from the solar plexus. They 

 follow the vessels in their distribution and are enclosed with them in the 

 capsule of Malpighi. They are distributed ultimately in the spleen- 



