THE SPLEEN. 337 



sustentacular cells possess ameboid movement, and in some of 

 them reddish granules, resembling hematin, are seen ; also red cor- 

 puscles in various stages of disintegration. In young spleens 

 Klein has seen these cells each with a large nucleus from which 

 project bud-like processes, and it has been suggested that these 

 are possibly white corpuscles in the process of formation. 



The Splenic artery enters the spleen at the hilum, after 

 having divided into a number of branches (Fig. 181) and being 

 covered by sheaths from the fibro-elastic coat. These arteries 

 divide and subdivide and finally end in the pulp in small arterioles, 

 their external coat gradually changing from connective tissue to 

 lymphoid tissue in which enlargements occur the Malpighian 

 corpuscles. These consist of a delicate reticulum enclosing lymph- 

 corpuscles. The cells which make up the reticulum possess ame- 

 boid movement. 



The arterioles end in capillaries, which later cease to be distinct 

 vessels, the cells making up their walls becoming branched and 

 the branches uniting with the processes of the sustentacular cells. 

 The blood which reaches the pulp through these vessels is by this 

 means brought into direct relation with it. It is again collected 

 into vessels which ultimately become veins that emerge from the 

 hilum as the splenic vein. 



Innervation of the Spleen The nerves which are dis- 

 tributed to the spleen are derived from the celiac plexus and right 

 vagus. 



Functions. The spleen has been frequently removed from 

 lower animals and from man. In the human being this operation, 

 splenectomy, is performed for wounds of the organ, " wandering 

 spleen " and enlargement due to malaria, and that accompanied 

 with anemia. Splenectomy, for enlargement associated with leuke- 

 mia, is accompanied with so much hemorrhage that it is, by excel- 

 lent authority, regarded as unjustifiable. 



In the chapter on " Surgery of the Lymphatic System," by 

 Prof. Warren in the International Text-Book of Surgery, the author 

 says that the results of the many operations already reported show 

 that the spleen is not an organ in any way essential to healthy 

 existence. A diminution in hemoglobin and in the number of red 

 corpuscles is a constant sequel to splenectomy in animals as in 

 man. This diminution reaches its height two to three weeks after 

 the operation, and then gradually disappears. There is also a 

 temporary leukocytosis, including the polynuclear form, the lym- 

 phocytes, and the eosinophiles. In some instances the lymph- 

 glands and the thyroid are enlarged, and an increased vascularity 

 of the bone-marrow occurs in animals. 



One of the most striking phenomena presented by the spleen is 

 the change in size which occurs during digestion. This begins after 

 a meal has been taken, and continues for about five hours, when the 

 maximum is reached, after which its decrease begins. This has 



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