CHAPTER X. 



THE SPLEEN, 

 BY WILHELM MULLEB, 



OF JENA. 



THE structure of the spleen is intimately associated with that 

 of the lymphatic glands. In both organs numerous trabeculae 

 proceeding from the capsule divide and subdivide, containing 

 in many animals muscular tissue, the contraction of which 

 effects a shortening of certain vascular channels and the eva- 

 cuation of the fluids contained in the parenchyma. In both 

 organs the cytogenous or adenoid tissue is employed to invest 

 at least a portion of the bloodvessels with sheaths containing 

 numerous cells, the rounded appendices of which, rich in capil- 

 laries, constitute the follicles of the lymphatic glands and the 

 so-called Malpighian corpuscles of the spleen. In both organs 

 the wall of certain vessels undergoes a peculiar modification, 

 characterised by the breaking up of the tissue into a plexus 

 of embryonal cells, the interstices of which are permeated by 

 the fluids contained in their respective vessels ; in the one case by 

 lymph, in the other by blood. It is a consequence of this agree- 

 ment in structure that certain causes of disease produce similar 

 pathological effects in both organs, as is seen in typhus, leucae- 

 mia, and certain forms of glandular sarcoma (Hodgkin's disease). 

 The spleen is not present in all Vertebrata. In the Lepto- 

 cardia and Myxinoids, for instance, it has not as yet been 

 demonstrated. In the remaining Vertebrata, which possess the 

 organ, it is constantly included between the laminae of the 

 peritoneum. Its position, however, is various; according to 

 whether it is developed in the meso-gastrium, the mesentery 

 proper, or the peritoneal investment of the pancreas. The 

 structure, again, presents varieties in the different classes of the 



