150 MICROSCOPIC ANATOMY OF THE ORGANS. 



According to Flint, lymphoitl nodules with germinal 

 centres are found sometimes in the medulla of the adrenal, and 

 scattered groups of lymphoid cells also in the cortex. 



Blood-vessels of the Adrenal. These, as they occur in the 

 dog, have been described in detail by Flint. In the capsule 

 the suprarenal arteries form a poorly defined plexus from 

 which the whole gland is supplied. Three systems of arteries 

 are derived from this plexus, supplying the capsule, cortex, and 

 medulla, respectively. The arteries capsulce form a network of 

 capillaries in the capsule, which empty into the capsular venous 

 plexus, which lies just beneath the arterial plexus. The 

 arterice corticis break up into a capillary plexus surrounding 

 the cell columns of the zona glomerulosa, from which the blood 

 flows into the parallel capillaries of the zona fasciculata, and 

 thence into the network of the zona reticularis. These capil- 

 laries empty into five veins which join to form the larger 

 trunks of the medulla. "The arterice medullce which run from 

 the capsule entirely through the cortex without anastomosing 

 break up into a capillary plexus in the medulla." The blood 

 flows from this plexus into the fine veins of the medulla, and 

 finally into the vena centralis. Usually two large venous 

 trunks are present in the medulla, one draining the anterior 

 and one the posterior lobe. These receive branches on all sides 

 from the peripheral parts of the medulla. The relations of 

 these vessels can be made out in Fig. 108. Lymph-vessels 

 form capillary networks around the cell columns. 



The framework of the adrenal has been described by Flint. 

 According to him, it consists of reticulum. That of the zona 

 glomerulosa consists of septa derived from the capsule. These 

 separate the coiled columns of cells making up this zone. The 

 framework of the zona fasciculata is made up of parallel strands 

 of reticulum running at right angles to the capsule. These 

 pass over into the framework of the zona reticularis, which 

 has the form of a spongy network of fibrils. The medulla 

 is supported by strands of reticulum which surround the cell 

 groups. 



Development of the Adrenal. It has been stated that the 



