i8io 



HUMAN ANATOMY. 



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

 disposed as clumps or cell-balls (Schaper 1 ) 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 chromaffinc 

 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 chromaffine cells likewise, since the nerve-fibres surround the groups of 



these elements. 



FIG. 1535. 



Carotid Body 



: :-::--& 



Capillaries 



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



In view of ( r ) the identity of its elements with other chromafnne cells, which 

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

 les, 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 2 concludes that since 

 the carotid body is neither a -land n<,r :i typical ganglion it must be regarded as acces- 

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

 name paraganglwn caroticum for the organ. Concerning its function nothing is 

 definitely known. 



The I >!<.... I vesM-U supplying the carotid body are branches which pass directly 

 .in other the common carotid artery or its terminal branches. 



THE COCCYGEAL BODY. 



Tliis Mj-M.m ("liuim*. o.a-M-1-iim i. also often called the coccv^caJ fland or 

 Ma *gl*** ( m honor <.t the anatomist who described it half a century ago 8 ), is 

 ..ill re, d.xh \,llou ovoid body which lies embedded in fatty areolar tissue usually 

 '" "'"' "I >'" 'p "i the coccyx, but sometimes just below. According 

 . \\ alker. .! M,,V,, guide to the body is the middle sjicral artery, to whose ante- 

 1 Aivhiv f. mikros. Anatomic, |! ( |. 40 1892 

 [Arcmv f. mikros. Anatomie, lid. 56 1900 



Die Hirn tnhang uml ,li,. Sh-isstlriise cfes Menschen. Berlin, 1860. 

 Arcliiv i. tnikros. An.itomie, Bd. 64 1904 



