98 DEVELOPMENT OF THE SPLEEN. 



itself, with a view to the renewal of its mobile cells ; and it does 

 this by causing the dilatation of circumscribed capillary areas at 

 various points, followed by the emigration of colourless blood-cor- 

 puscles. The number of the emigrant cells subsequently increases 

 by fission, and this increase continues to add to the bulk of the 

 glandular parenchyma so long as efferent canals for the removal 

 of the superfluous cells are lacking. At a later period a certain 

 equilibrium is established between the production and the 

 removal of the cells — an equilibrium which can only be disturbed 

 by pathological irritants.* 



§ 77. The SPLEEN ranks with the lymphatic glands in its 

 genetic history. The " formation of lymphatic sheaths," as the 

 local emigration of colourless corpuscles and their accumulation 

 round the vessels is usually termed — a phenomenon which my 

 own observations have led me to adopt as the most probable 

 mode of development of the lymphatic glands — is carried a step 

 farther in the case of the spleen. In this organ, as in the lymphatic 

 glands, the vessels begin by surrounding themselves with lym- 

 phatic sheaths, which here receive the name of Malpighian 

 corpuscles. The vascular walls then undergo perforation, and 

 split up into fibres. In this wise a delicate spongy tissue is formed, 

 through which the blood percolates, to be again collected on the 

 opposite side of the filter by efferent veins, which permeate the 

 spongy tissue in all directions. The function of the spleen is 

 environed by the same doubts and conflicting opinions as that of 

 the lymphatic glands, save that the splenic pulp is held to be at 



* I cannot refrain from calling the reader's attention to the valuable 

 analogies presented by the development of the lymphatic glands (as 

 described above) to the many formative disorders of the intermediate 

 apparatus of nutrition {see next chapter). In the latter as in the former 

 case, migration of cells, followed by their fission, underlies all formative 

 activity. Emigration brings the cells into contact with the tissues, and 

 affords them a comparative measure of repose; and these conditions 

 seem to determine first their amoeboid motility, and secondly their fissi- 

 parous multiplication. I am convinced however, that fission rather than 

 migration is the proximate and effective cause of inflammatory production 

 and the growth of histioid tumours. To this is due the colossal size 

 which these tumours may attain, such enormous increase depending on 

 the inadequate development of the lymphatics, which are thus unable to 

 provide, as they do in the case of the lymphatic glands, for the due 

 removal of the excess of cells. 



