458 THE DUCTLESS GLANDS 



In certain instances the epithelial cells are arranged in small 

 alveolar groups which are surrounded by a network of capillary 

 vessels. This arrangement appears to be more frequent in young 

 individuals. The cell groups in this type of gland frequently 

 form branching columns. 



Occasionally, epithelial cells surround a central lumen, in 

 which are small masses of an acidophile substance which re- 

 sembles colloid in its reactions. In the experience of the author 

 this colloidal material is less abundant in the human parathyroid 

 than in that of the lower mammals. Likewise the cystic ducts, 

 lined by columnar or ciliated columnar epithelium, which have 

 been described by Kohn,* though of frequent occurrence in the 

 lower mammals are rarely, if ever, found in the human parathyroid. 



The connective tissue of the gland is of variable quantity. It 

 forms a thin but dense capsule ; occasionally trabeculae extend 

 inward and partially outline indistinct lobules. In many instances 

 a hilum transmits the larger bloodvessels by means of vascular 

 trabeculae which radiate to all portions of the organ. A delicate 

 fibrous or reticular stroma invests the individual cells, or the cell 

 groups, when these are present. Occasionally the cells are so 

 closely packed that the stroma is scarcely demonstrable. 



The blood supply of the parathyroid is exceedingly rich. 

 Arteries enter from the capsule, or at the hilum, and rapidly break 

 up into a plexus of broad capillary or sinusoidal vessels which 

 follow the fibrous bands of the stroma and are in intimate relation 

 with the epithelium. They are collected into thin-walled venules 

 which retrace the course of the arteries. 



IV. THE CAROTID GLAND 



This body was first carefully described by Luschka f and, from 

 its intimate relation to the blood vessels and nerves, is also known 

 as the glomus caroticum or ganglion inter car oticum. It consists 

 of scattered masses of epithelial cells, usually grouped in small 

 spheroidal clumps or "cell balls" embedded in the connective 

 tissue. Kohn { has described four types of the gland according to 

 the density of its parenchyma the type found in man consists 

 of scattered cell groups ; in the rabbit they are even more diffuse. 

 The carotid gland of a cat consists of a single cell mass, while that 

 of the ape is intermediate between that of the cat and man. 



* Arch. f. mik. Anat., 1897. f Arch. f. Anat., 1862. 



J Arch. f. mik. Anat., 1900. 



