1080 



THE ORGANS OF DIGESTION. 



If 



looser and laxer, their fibrils more delicate, and containing in their interstices 

 an abundance of lymph-corpuscles (W. Miiller). This lymphoid material is 

 supplied with blood by minute vessels derived from the artery with which they 

 are in contact, and which terminates by breaking up into a network of capillary 

 vessels. 



The altered coat of the arterioles, consisting of lymphoid tissue, presents here 

 and there thickenings of a spheroidal shape, the Malpiyliian bodies of the spleen. 

 These bodies vary in size from about the yj-^ of an inch to the -^ of an inch in 

 diameter. They are merely local expansions or hyperplasise of the lymphoid 

 tissue of which the external coat of the smaller arteries of the spleen is formed. 

 They are most frequently found surrounding the arteriole, which thus seems to 



tunnel them, but occasionally they grow from 

 one side of the vessel only, and present the 

 appearance of a sessile bud growing from the 

 arterial wall. Klein, however, denies this, 

 and says it is incorrect to describe the Mal- 

 pighian bodies as isolated masses of adenoid 

 tissue, but that they are always formed around 

 an artery, though there is generally a greater 

 amount on one side than the other, and that, 

 therefore, in transverse sections the artery in 

 the majority of cases is found in an eccentric 

 position. These bodies are visible to the naked 

 eye on the surface of a fresh section of the 

 organ, appearing as minute dots of semi- 

 opaque whitish color in the dark substance 

 of the pulp. In minute structure they re- 

 semble the adenoid tissue of lymphatic glands, 

 consisting of a delicate reticulum in the meshes 

 of which lie ordinary lymphoid cells (Fig. 



The reticulum of the tissue is made up 

 of extremely delicate fibrils, and is comparatively open in the centre of the 

 corpuscle, becoming closer at the periphery of the body. The cells which it 

 encloses, like the supporting cells of the pulp, are possessed of amoeboid move- 



Arte>-y 



FIG. 690. Artery from a dog's spleen, 

 showing Malpighian corpuscles. (Kolliker.) 



Supporting cell. 



Vessel undergoing lymphoid change. 



' 



Small 

 artery. ' 



Vessel continuous 

 loith procesw of 

 supporting cells. 



Supporting cell. 



FIG. 691. Section of spleen, showing the termination of the small blood-vessels. 



ments, but when treated with carmine become deeply stained, and can thus 

 easily be recognized from those of the pulp. 



The arterioles terminate in capillaries, Avhich traverse the pulp in all directions ; 



