950 THE ORGANS OF DIGESTION. 



and lesser sacs, respectively, where they meet between the spleen and stomach 

 (Fig. 489). Between these two layers run the vasa brevia of the splenic artery 

 and vein. It is also supported by the phreno-colic ligament, upon which its lower 

 end rests (see page 902). 



The size and weight of the spleen are liable to very extreme variations at dif- 

 ferent periods of life, in different individuals, and in the same individual under 

 different conditions. In the adult, in whom it attains its greatest size, it is usually 

 about five inches in length, three inches in breadth, and an inch or an inch and a 

 half in thickness, and weighs about seven ounces. At birth, its weight, in propor- 

 tion to the entire body, is almost equal to what is observed in the adult, being as 

 1 to 350 : while in the adult it varies from 1 to 320 and 400. In old age, the 

 organ not only decreases in weight, but decreases considerably in proportion to 

 the entire body, being as 1 to 700. The size of the spleen is increased during and 



FIG. 523. Transverse section of the spleen, showing the trabecular tissue and the splenic vein and its trib- 

 utaries. 



after digestion, and varies considerably according to the state of nutrition of the 

 body, being large in highly fed, and small in starved animals. In intermittent 

 and other fevers it becomes much enlarged, weighing occasionally from 18 to 20 

 pounds. 



Frequently in the neighborhood of the spleen, and especially in the gastro- 

 splenic and great omenta, small nodules of splenic tissue may be found, either 

 isolated or connected to the spleen by thin bands of splenic tissue. They are 

 known as supernumerary or accessory spleens. They vary in size from that of a 

 pea to that of a plum. 



Structure. The spleen is invested by two coats an external serous, and an 

 internal fibro-elastic coat. 



The external or serous coat, is derived from the peritoneum ; it is thin, smooth, 

 and in the human subject intimately adherent to the fibro-elastic coat. It invests 

 the entire organ, except at the places of its reflection on to the stomach and 

 Diaphragm and at the hilum. 



The fibro-elastic coat forms the framework of the spleen. It invests the organ, 

 and at the hilum is reflected inward upon the vessels in the form of sheaths. 

 From these sheaths, as well as from the inner surface of the fibro-elastic coat, 

 numerous small fibrous bands, trabeculce (Fig. 524), are given off in all directions ; 

 these uniting, constitute the framework of the spleen. This resembles a sponge- 

 like material, consisting of a number of small spaces or areolce formed by the tra- 

 beculae, which are given off from the inner surface of the capsule, or from the 



