416 USES OF THE LIVER DUCTLESS GLANDS. 



The splenic artery is the largest branch of the cceliac axis. It is a vessel of con- 

 siderable length and is remarkable for its tortuous course. In an observation 

 by Sappey, in a man between forty and fifty years of age, the vessel measured 

 about five inches (12 centimetres), without taking account of its deflections; 

 and a thread placed on the vessel so as to follow exactly all its windings meas- 

 ured a little more than eight inches (21 centimetres). The large caliber of 

 this vessel and its tortuous course are important points in connection with 

 the great variations in the size of the spleen under various conditions in health 

 and disease. The artery gives off several branches to the adjacent viscera in 

 its course, 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 sub- 

 stance of the spleen, with the veins, nerves and lymphatics, enveloped in 

 fibrous sheaths. In the substance of the spleen the arteries branch rather 

 peculiarly, giving off many small ramifications in their course, generally at 

 right angles to the parent trunk. These are accompanied by the veins until 

 they are reduced to -fa or -fa of an inch (0'32 or 0-42 mm.) 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 caliber is estimated as 

 about twice that of the arteries (Sappey). The estimates which have put 

 the caliber of the veins at four or five times that of the arteries are probably 

 much 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 recognized, 

 the superficial and the deep. The superficial lymphatics are in the investing 

 membrane of the spleen and probably are connected with the deep lym- 

 phatics. The origin of the deep vessels is somewhat obscure. Lymphatic 

 spaces or sinuses surround the Malpighian bodies, and there is probably a 

 perivascular canal-system, the exact origin of which is unknown. At the 

 hilum the deep lymphatics are joined by vessels from the surface. The ves- 

 sels, 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-pulp, but nothing 

 definite is known of their mode of termination. When these nerves are 

 stimulated, the non-striated muscles in the substance of the spleen are thrown 

 into contraction. 



Some Points in the Chemical Constitution of the Spleen. Very little has 

 been learned with regard to the probable uses of the spleen from analyses of 

 its substance ; and it would therefore be out of place to discuss its chemical 



