THE CAROTID AND COCCYGEAL BODIES 251 



in the human subject. He suggests the name " nodulus 

 caroticus," and considers the body in question to be a rudi- 

 mentary organ. 



Stilling made the important discovery that the carotid body 

 contains some cells which stain brown with potassium bichro- 

 mate. This observation was confirmed by Kohn, who has 

 added to the long list of names attached to this tiny body, by 

 suggesting that it be called the " paraganglion intercaroticum." 



Comparative Anatomy and Embryology 



In the human subject the carotid glands are small bodies 

 situated just above the bifurcation of the common carotid 

 artery on each side, and between its internal and external 

 branches. According to Luschka, the gland is of an elongated 

 spherical shape, 5 to 7 millimetres long, 4 to 2J millimetres 

 broad, and 1J millimetres thick. Sometimes it is divided into 

 two or more nodules. The body is greyish or brownish-red 

 in colour. Its consistence is more compact than that of a 

 nerve ganglion, and its substance cannot be easily teased out 

 with needles. 



In all, or in nearly all mammals so far investigated, the 

 carotid body has been found in the neighbourhood of the 

 bifurcation of the common carotid artery, either exactly at the 

 bifurcation or somewhat higher up in the connective tissue 

 between the internal and external carotid arteries. Both 

 these and the common carotid may give twigs to the body. 



Many observers have noted the richness of the nerve-supply 

 to the carotid body ; this supply is mostly from the sympathetic 

 nervous system. According to Luschka, there is situated 

 between the internal and the external carotid arteries a rich 

 nervous plexus beset with tiny ganglia plexus intercaroticus 

 which is a complex of fibres from the superior laryngeal and 

 the glosso-pharyngeal nerves, and a variable number of twigs 

 from the superior cervical ganglion. According to Svitzer, 

 there are twigs to the body from the superior cervical ganglion, 

 from the nervi molles Halleri, from the trunk and the pharyn- 

 geal branch of the vagus, from the superior laryngeal branch 

 of the vagus, from the hypoglossal, and from the sympathetic 

 above and below the superior cervical ganglion. 



According to Maurer, the body is absent in fishes, but present 

 in Amphibians and all higher vertebrates. In the Anura an 



