STRUCTURE OF THE SUPRARENAL CAPSULES. 189- 



which has passed into its interstices from the arterial capillaries 

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

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

 first conducted from the hilum along the trabeculse into the interior of 

 the organ, presently leave the trabeculss, 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 manner before described. 



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

 peculiar, large, amceboid cells, 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 capsule,, 

 and partly in the lymphoid tissue eiisheathing the arteries. They join 

 to form larger vessels which emerge together at the hilum. 



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. 222) 



FIG. 222. A VERTICAL SECTION OF THE SUPRARENAL BODY OF A FCETUS, TWICE 



THE NATURAL SIZE, SHOWING THE DISTINCTION BETWEEN THE MEDULLARY 

 AND CORTICAL SUBSTANCE. (A. Thomson.) 



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. 

 223), subdividing this for the most part into columnar groups of cells. 



