STRUCTURE OF THE SUPRARENAL CAPSULES 161 



towards the larger veins of the organ, which run in the trabeculae, and 

 are by them conducted to the hilus. The arteries, which are also at 

 first conducted from the hilus along the trabeculae into the interior of 

 the organ, presently leave the trabeculae, and their external coat 

 becomes converted into a thick sheath of lymphoid tissue which invests 

 them in the remainder of their course, and in places becomes swollen 

 into the Malpighian corpuscles already mentioned. These small 

 arteries distribute a few capillaries to the Malpighian corpuscles, and 

 then break up into pencils of small vessels which open into the pulp in 

 the mariner already mentioned. 



The cellular elements of the spleen-pulp are of three kinds, viz. 

 large, amoeboid, connective-tissue cells, also called splenic cells, lymph- 

 corpuscles, and the branched, flattened cells which form the sponge- 

 work. The first-named are frequently found to contain coloured 

 blood-corpuscles in their interior in various stages of transformation 

 into pigment. 



The lymphatics of the spleen run partly in the trabeculae and cap- 

 sule, and partly in the lymphoid tissue ensheathing the arteries. They 

 join to form larger vessels which emerge together at the hilus. 



THE SUPRARENAL CAPSULES. 



The suprarenal capsules belong to the class of bodies known as duct- 

 less glands, but they are entirely different in structure from the spleen 

 and lymphatic glands. A section through the fresh organ (fig. 195) 



FlG. 195. A VERTICAL, SECTION OF THE SUPRARENAL BODY OF A FCETUS, TWICE 

 THE NATURAL SIZE, SHOWING THE DISTINCTION BETWEEN THE MEDULLARY 

 AND CORTICAL SUBSTANCE. 



v, issuing vein ; r, summit of kidney. 



shows a cortical zone which is striated vertically to the surface, and of a 

 yellowish colour, and a medulla which is soft and highly vascular, and 

 of a brownish-red colour. The whole organ is invested by a fibrous 

 capsule which sends fibrous septa inwards to the cortical substance 

 (fig. 196), subdividing this for the most part into columnar groups of cells 

 (zona fasciculata, c\. Immediately underneath the capsule, however, 



