SEC. 2. THE SPLEEN. 



372. The Movements of the Spleen. A salient structural 

 feature of the spleen is, that many of the minute arteries open 

 out into the labyrinths of the coarse reticulum which occupy 

 the irregular chambers marked off by the trabeculae; blood 

 passes bodily into the spaces between the branched cells of the 

 reticulum. The amount of blood which thus travels slowly 

 through or even for a while tarries in the meshes of the retic- 

 ulum, forming the so-called 4 4 spleen-pulp, " as compared with 

 the amount which traverses the spleen in the ordinary way 

 confined to the closed channels of the capillaries, varies from 

 time to time according to the condition of the organ. For the 

 spleen is subject to changes leading to considerable variations 

 in its volume. 



After a meal the spleen increases in size, reaching its maxi- 

 mum about five hours after the taking of food; it remains 

 swollen for some time, and then returns to its normal bulk. 

 In certain diseases, such as in the pyrexia attendant on certain 

 fevers or inflammations, and more especially in ague, a somewhat 

 similar temporary enlargement takes place. In prolonged ague 

 a permanent hypertrophy of the spleen, the so-called ague-cake, 

 occurs. 



The turgescence of the spleen seems to be due to a relaxation 

 both of the small arteries and of the muscular tissue of the cap- 

 sule and of the trabeculae; to be, in fact, a vascular dilation 

 accompanied by a local inhibition of the tonic contraction of 

 the other plain muscular fibres entering into the structure of 

 the organ, the latter, at all events in some animals, being prob- 

 ably the more important of the two. And the condition of the 

 spleen, like that of other vascular areas, appears to be regulated 

 by the central nervous system, the digestive turgescence being 

 fairly comparable to the flushed condition of the pancreas and 

 of the gastric membrane during their phases of activity. 



The application of the plethysmographic method to the 

 spleen, carried out in the way which we described in speaking 

 of the kidney ( 380), enables us to study more exactly the 

 variations in volume which the organ undergoes. 



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