i8io 



HUMAN ANATOMY. 



plex of blood-vessels, nerve-fibres and peculiar cells. The latter are irregularly, 

 disposed as clumps or cell-balls (Schaper^) and occupy the interspaces within the 

 close net-work of large capillaries which ramify among the cells. The characteristic 

 elements of the carotid body are the polygonal cells, about .01 mm. in diameter, 

 with large round nuclei. Their protoplasm is finely granular and is especially prone 

 to change, being best preserved in solutions of chromic acid salts. When so treated, 

 they take on the peculiar yellow color entitling them to be classed as chroniaffiiie 

 cells. The large number of nerve-fibres within the carotid body is remarkable. They 

 are mostly nonmedullated and are derived chiefly from the neighboring sympathetic 

 plexus surrounding the carotid artery and, after entering at different places, ramify 

 within the organ in all directions, the finest filaments being lost among the groups of 

 cells. The penetrating nerve-trunks usually enclose typical ganglion-cells and, in a 

 sense, the chromafifine cells likewise, since the nerve-fibres surround the groups of 



these elements. 



Fig. 1535. 



Capillaries 



Capsule 



Section of adult human carotid body ; one entire lobule is shown. X 170. 



In view of ( i ) the identity of its elements with other chromafiine cells, which 

 are now recognized as closely associated with the sympathetic system in other locali- 

 ties, as in the medulla of the suprarenal body, (2) its extraordinary richness in nerve- 

 fibres, (3) its general resemblance to a sympathetic ganglion, and (4) its direct 

 development from embryonal sympathetic ganglion cells, Kohn ^ concludes that since 

 the carotid body is neither a gland nor a typical ganglion it must be regarded as acces- 

 sory to the sympathetic system and, in recognition of this relation, proposes the 

 name paraganglion caroticuvi for the organ. Concerning its function nothing is 

 definitely known. 



The blood-vessels supplying the carotid body are branches which pass directly 

 from either the common carotid artery or its terminal branches. 



THE COCCYGEAL BODY. 



This organ (glomus coccygcum ), also often called the coccygeal gland, or 

 Luschka s gland (in honor of the anatomist who described it half a century ago''), is 

 a small reddish yellow ovoid body which lies embedded in fatty areolar tissue usually 

 immediately in front of the tip of the coccyx, but sometimes just below. According 

 to Walker,* the surest guide to the body is the middle sacral artery , to whose ante- 



^ Archiv f. mikros. Anatomic, Bd. 40, 1892. 



^Archiv f. mikros. Anatomic, Bd. 56, 1900. 



^ Die Hirnanhan": und die Stcissdriise des Menschcn. Berlin, i860. 



■* Archiv f. mikros. Anatomic, Bd. 64, 1904. 



