THE CAROTID BODY. 



117 



constricted and eventually separated. Others are seemingly independent 

 masses of splenic tissue. Not a few have no splenic nodules and are inter- 

 mediate between the spleen and the lymph-nodes, and, probably, are to be 

 classed as hemolymph nodes. 



As a matter of convenience, mention may be made at this place of two 

 organs the carotid and the coccygeal bodies concerning whose functions 

 little or nothing is known. The systematic position of these structures is at 

 present uncertain, but, from its histological characteristics, the carotid 

 body is probably to be regarded as closely related to or, in a sense, an 

 appendage of the system of sympathetic nerves, whilst the coccygeal body 

 may be included, with doubtful propriety, with the organs of internal secre- 

 tion. Their grouping and description here, therefore, must be understood 

 to be a matter of convenience and expediency and not an attempt to define 

 their true relations. 



THE CAROTID BODY. 



This organ, also known as the glomus caroticum, carotid gland and 

 ganglion intercaroticum, is a small ovoid body measuring usually about 

 5 mm. in length, from 2.5-4 mm. in width and about 1.5 mm. in thickness. 



Capillaries 



Capsule 



FIG. 157. Section of carotid body of adult man ; one entire lobule is shown. X 17- 



It may attain a length of 7 mm. and exists on both sides. Its most frequent 

 position is on the median and deep side of the upper end of the common 

 carotid artery in close relation with the point of division of the latter vessel 

 into the external and internal carotids. The body usually lies not within the 

 bifurcation, but rather on the inner side of the common carotid, so that its 

 form and relations are best displayed by dissection from within outwards. 



The body is surrounded by a thin fibrous capsule, from which delicate 

 septa penetrate inwards and divide the organ into a small and uncertain 

 number (5-15) of spherical masses or lobules, from .2-. 5 mm. in diameter, 

 which consist of a complex of blood-vessels, nerve-fibres and peculiar cells. 



