THE VASCULAR GLANDS. 393 



The Coccygeal and Carotid Glands. 



These so-called glands are situated, the one in front of the tip of the 

 coccyx, and the other at the point of bifurcation of the common carotid 

 artery on each side. They are made up of a plexus of small arteries, 

 are inclosed and supported by a capsule of fibrous tissue, which contains 

 connective-tissue corpuscles. The blood-vessels are surrounded by one 

 or more layers of cells like secreting-cells, which are said to be modified 

 plasma-cells of the connective tissue. The function of these bodies is 

 unknown. 



Functions of the Vascular Glands in General. 



The opinion that the vascular glands serve for the higher organiza- 

 tion of the blood, is supported by their being all especially active in the 

 discharge of their functions during foetal life and childhood, when, for 

 the development and growth of the body, the most abundant supply of 

 highly organized blood is necessary. The bulk of the thymus gland; in 

 proportion to that of the body, appears to bear almost a direct propor- 

 tion to the activity of the body's development and growth, and when, at 

 the period of puberty, the development of the body may be said to be 

 complete, the gland wastes, and finally disappears. The thyroid gland 

 and supra- renal capsules, also, though they probably never cease to dis- 

 charge some function, yet are proportionally much smaller in childhood 

 than in foetal life and infancy; and with the years advancing to the adult 

 period, they diminish yet more in proportionate size and apparent ac- 

 tivity of function. The spleen more nearly retains its proportionate 

 size, and enlarges nearly as the whole body does. 



Although the functions of all the vascular glands may be similar, in 

 so far as they may all alike serve for the elaboration and maintenance of 

 the blood, yet each of them probably discharges a peculiar office, in re- 

 lation either to the whole economy, or to that of some other organ. 

 Eespecting any special office of the thyroid gland, nothing reasonable 

 has been hitherto suggested; nor is there any certain evidence concern- 

 ing that of the supra-renal capsules, Bergman believed that they 

 formed part of the sympathetic nervous system from the richness of 

 their nervous supply. Kolliker looked upon the two parts as function- 

 ally distinct, the cortical part belonging to the blood vascular system, 

 and the medullary to the nervous system. 



