306 SECRETION 



The spleen is attached to the stomach by the 

 gastrosplenic omentum. The lienorenal ligament is a 

 peritoneal fold, which attaches it to the upper pole of 

 the left kidney, and the phrenocolic assists to support 

 it by its attachment to the diaphragm. 



The spleen when seen under the microscope shows 

 a capsule of fibrous tissue which sends off slips or 

 trabeculse from its under surface; these spread out 

 and form a connective-tissue supporting frame-work 

 for the contents of the organ, which consists of a 

 dark red semifluid mass called the splenic pulp, filling 

 the spaces between the fibrous tissue. Microscopically 

 the splenic pulp is seen to consist of adenoid tissue, 

 rich in leukocytes or white-blood cells, arranged in 

 small groups throughout the pulp, called Malpighian 

 corpuscles; red corpuscles are also present in the pulp. 



The Functions of the Spleen. Owing to the numbers 

 of red cells seen in the splenic pulp undergoing all 

 stages of disintegration, it has been concluded that 

 the spleen aids in the destruction of red cells; another 

 theory is based on the presence of the large quantity 

 of white cells within the Malpighian corpuscles, that 

 the spleen is the chief centre for the production of 

 white cells, and thus contributes to the formation of 

 the blood. 



The spleen is larger in childhood than old age; 

 it is enlarged during and after digestion. In typhoid 

 fever and malaria a marked increase can be noted; 

 also in various blood diseases. 



Thymus Gland. The thymus gland is a temporary 

 organ, attaining its full size at the end of the second 

 year and gradually shrinking until puberty, when 

 it entirely disappears. Consists of two lateral lobes 

 placed in close contact along the median line. It 

 is found in the superior mediastinum, covered by the 

 sternum and the origins of the sternohyoid and sterno- 

 thyroid muscles; below, it rests upon the pericardium, 

 and separated from the arch of the aorta and great 



