THE CAROTID GLAND. 



225 



Mention has been made of the migration of leucocytes and, 

 under certain conditions, of red blood-cells through the walls of 

 blood capillaries, and in the case of the former through the walls of 

 lymph capillaries and lymph-vessels and spaces. This diapedesis of 

 leucocytes probably takes place by a wandering of these cells 

 through the intercellular cement uniting the endothelial cells lining 

 these spaces. According to later investigations, it would seem that 

 leucocytes may bore through endothelial cells, and thus migrate 

 from the vessel or space in which they are found previous to such 

 migration. 



C THE CAROTID GLAND (GLANDULA CAROTICA, 

 GLOMUS CAROTICUM). 



At the point where the common carotid divides, there lies in 

 man a small oval structure about the size of a grain of wheat, known 

 as the carotid gland or the glomus caroticum. It is imbedded in 



^ Septum. 



Trabecula of 

 cells in cross- 

 section. 



Distended 

 blood capil- 

 laries. 



_. Efferent vein. 



Fig. 178. Section of a cell-ball from the glomus caroticum of man ; X I ^- (Injected 

 specimen, after Schaper.) 



connective tissue, surrounded by many nerve-fibers, and on account 

 of its great vascularity has a decidedly red color. The connective- 

 tissue envelope of the gland penetrates into the interior in the form 

 of septa, which divide its substance into small lobules, and these in 

 turn into smaller round masses, the cell-balls. A small branch 

 from the internal or external carotid enters the gland, where 

 it branches, sending off twigs to the lobules, and these in turn still 

 15 



