554 THE DUCTLESS GLANDS ENDOCRIN GLANDS 



acter; in other cells they consist of a dense, almost solid, mass of chro- 

 matin. The shape of the cell groups in the medulla varies greatly; 

 usually they form small spheroidal masses or short columns. The cells 

 are frequently arranged in~a~more or less tubular form but without 

 a distmcjJ*H*reii. Frequently they surround a minute" capillary vessel. 

 The medullary cells presumably pour their secretion into the blood- 

 vessels, whose broad sinusoidal capillaries permeate the delicate connec- 

 tive tissue bands which inclose the cell groups. Felicine (Arch. f. mikr. 

 Anat., 1904) claims to have demonstrated the presence of minute intra- 

 and intercellular secretory canaliculi which open directly or indirectly 

 through broader lacunce, into\ the blood-vessels. 



The cell groups of the mecTtifWlike those of the cortex, are divisible 

 into the acidophil and the fatM types; the former are the more abun- 

 dant, but the fatty metamorphosis is scarcely ever so advanced as in the 

 cortex. There is, however, great variation in the size of the medullary 

 cells. The larger ovoid elements form the typical groups; between 

 these groups are narrow cell colLmns consisting of much smaller and 

 less highly acidophil cells, which \ are arranged in slender columns and 

 scattered irregular masses. 



The striking feature of the mequllary cells is their granular content. 

 These chromaffin granules have a Special affinity for chromic acid and 

 its salts, and stain a light brown or yellow. Their staining capacity in 

 chromium solutions is due to the l presence of adrenalin (Kingsbury, 

 Anat. Rec., 5, 1, 1911). The granules are very readily soluble in acids. 



In the vicinity of the central vlins, small nerve trunks are found, 

 and occasional minute ganglia or isolated nerve cells occur along their 

 course. These are not to be confusedlwith the large ovoid epithelial cells 

 of the medulla. 



Blood Supply. The arteries which^supjply .tha^uprarenal glands 

 form a p]eW_pJ_^esselsin the_capsulejof the organ and in the neighbor- 

 ing connective tissue. Some of the 'smaller branches of this plexus, the 

 capsular arteries, supply the capsule itself, others enterjhe organ and 

 are distributed to the cortex and to the medulla^ The blood supplied 

 to the oapsnlar arteries, after traversing the capillaries, enters small 

 venules which are tributary to the lumbar and phrenic veins. The course 

 of the cortical and medullary vessels has been exhaustively studied by 

 Flint (Proc. Bost. Soc. of Nat. Hist, 1900). 



The cortical arteries enter the zona glomerulosa where they abruptly 

 break up to form a capillary plexus which occupies the connective tissue 

 between the cell columns. Capillary vessels are continued from this 



