CHAPTER III. 



THE SPLEEN AND THYMIIS. 

 The Spleen. 



General Characteristics of the Spleen. 



IN studying the lesions of the spleen it is important to bear in mind the peculiai 

 relations in which this organ stands to the blood-vessels and to the circulation. After 

 passing through the various branches of the splenic artery and the limited systems of 

 capillaries which are associated with it, the blood is not received at once into venous 

 trunks, as in other parts of the body, but is poured directly into the pulp tissue. In 

 this it circulates, under conditions which render it liable to stagnation and undue accu- 

 mulation, before it is taken again into well-defined vessels through the open walls of 

 the cavernous veins. Moreover, these conditions, naturally unfavorable to undisturbed 

 and vigorous circulation, are reinforced by the association of the splenic with the slug- 

 gish and often interrupted portal circulation. Bearing these considerations in mind, it 

 is in a measure plain why, as is in fact the case, the spleen should be more liable to 

 alterations in size than any other organ in the body, and why, serving as it does as a 

 sort of blood filter, it should be especially susceptible to the influence of deleterious 

 materials of various kinds which in one way or another gain access to the blood. The 

 relationship between the lymph-vessels and the spleen is also intimate. 



Malformations and Displacements. 



The spleen may be absent in acephalous monsters, and with defective development 

 of other abdominal viscera. Absence of the spleen in otherwise normally developed 

 individuals has been recorded. There may in this condition be a compensatory hyper- 

 plasia of the lymphatic tissues of the body. 1 Small accessory spleens, from the size of 

 a hazelnut to that of a walnut, are not infrequent. They usually lie close to the spleen, 

 but may be at a considerable distance from it ; thus they have been found embedded in 

 the head of the pancreas.' 2 Two spleens of about equal size have been observed. The 

 spleen may be made up of several distinct lobes. It may be displaced congenitally or 

 as the result of disease. It may be on the right side in transposition of the viscera. As 

 the result of congenital defects in the diaphragm the spleen may be found in the thorax ; 

 or in deficient closure of the abdominal wall it may, together with other abdominal vis- 

 cera, be found outside of the body. 



The spleen may be pressed downward by any increase in the contents of the thorax. 

 It may be bound by adhesions to the concave surface of the diaphragm, so that its long 

 axis is nearly horizontal instead of vertical. It may be displaced by changes in the 

 contents of the abdominal cavity. If the organ be increased in size it frequently be- 

 comes tilted, so that its lower border reaches the right iliac region. If the ligaments be 

 too long congenitally, or if they are lengthened by traction, and if the organ is at the 

 same time increased in weight, it may become very movable. It may sink downward, 

 with its hilus turned upward; or it may be rotated on its axis, and, owing to torsion of 

 the vessels thus produced, the organ may atrophy; or the pressure of the ligaments and 

 vessels across the duodenum may cause occlusion of the gut. 



1 See Hodenpyl, Med. Record, November 12th, 1898, bibl. For a study of the effect 

 of spleneetomy in animals on the hoemolymph nodes see Warthin, " Vaughan Anniver- 

 sary Contributions to Med. Research," 1903, p. 216. 



2 ttemolymph nodes may be mistaken for accessory spleens. 



