THE SPLEEN 



1311 



20 gm. On the other hand, spleens weighing 3000 to 4000 gm. are sometimes fomid. These are 

 usually, however, associated with an acute infectious disease, such as malaria or typhoid fever, 

 or a progressive metamorphosis, such as leukemia. 



Congenital absence of the spleen is one of the rarest anomahes. The presence of more than 

 one spleen is the commonest anomaly of the spleen. Adami has found accessory spleens to 

 occur in 11 per cent, of all autopsies. They are round or oblong and vary in size from a pea, or 

 smaller, to a walnut. There are most often one or two but there may be twenty or more. 

 They are found near the hilus on the dorsal side of thegastrohenal ligament, less often, in the 

 great omentum, in the mesentery, on the wall of the intestine, or in the tail of the pancreas. 



In certain cases the left lobe of the liver is very long and prolonged far to the left and sepa- 

 rates the spleen from the diaphragm. This is the rule in the fcetus and is often found in the 

 infant but is exceptional in the adult. 



Exceptionally the spleen may be placed far caudal to the normal situation extending into 

 the iUac region and even into the pelvis. This is due in part to congenital laxness of the supports, 

 also to increase in weight. The spleen has been found in almost every part of the abdominal 

 cavitj' and in transposition of the viscera it is upon the right side. 



One or more notches on the anterior border are present according to Parsons in 93 per cent, 

 of the cases, two or more in 66 per cent., but five, six, or seven much more rarely. On the pos- 

 terior border notches are foimd in 32 per cent, of the cases, and on the inferior border in 8 per 

 cent. In 20 per cent, of the cases a marked fissure, occasionally more than one, is found on the 

 diaphragmatic surface. Most frequently it begins at one of the notches in the posterior border 

 and passes for a distance across the surface, rarely reaching the anterior border. Occasionally 

 such a fissure starts from the anterior border and rarely there is such a fissure connecting with 

 neither border. 



Fig. 1067.- 



-Portion of Section of the Spleen of an Adult Man. 



''Lewis anil Stolir.) 



X 15. 



Capsule (tunica 

 albuginea) 



Splenic pulp 



y 



TrabeculEB lienis 



?»4'l 



spindle-shaped nodule 



> 



Central arteries in 

 splenic nodules 



Arteries<x^ 



Structure. — The peritoneal covering of the spleen, tunica serosa, is intimately 

 bound to the underlying, whitish, highly elastic fibrous capsule, the tunica albu- 

 ginea (fig. 1067). This is composed mainly of white fibrous connective tissue but 

 contains numerous fine elastic fibers, and a few smooth muscle fibres. It is much 

 thicker than the serous covering and completely invests the spleen. From its 

 deep surface the tunica albuginea gives off into the interior numerous trabeculse, 

 trabeculae lienis, which join with one another and form a framework in which 

 course the blood-vessels, more especially the veins. It is through the contraction 

 of the smooth muscle fibres in the tunica albuginea and trabeculse, that the regular 

 periodic contraction and expansion of the spleen is produced. 



In the meshes of the trabecular network, Ij^mphoid tissue which forms the 

 proper splenic tissue, the pulpa lienis, is located. This is soft, friable, and dark 

 brownish or bluish-red in colour. In this, in a fresh spleen, are seen small round 

 whitish or greyish masses from .25 to 1.5 mm. in diameter, the Malpighian cor- 

 puscles [noduli lymphatici lienales; Malpighii]. 



The trabeculse are in connection with a reticular network which permeates the spleen sub- 

 stance or spleen-pulp. Mall has shown that the trabeculse and vascular system together out- 



