523 INTIMATE STRUCTURE OF THE THYMUS GLAND. 



front, through which passes up the cervical portion of the 

 thymus gland. 



— The gland consists of two halves, connected in the middle 

 by cellular tissue only, which may properly be called a right 

 and left lobe. According to Sir A. Cooper, who has published 

 a beautiful monograph on the structure of this organ, the 

 gland grows gradually with the increasing growth of the foetus, 

 till the seventh month. During the ninth- it is suddenly and 

 greatly increased in size, and at birth weighs tw^o hundred 

 and forty grains. It continues to enlarge till the end of the 

 first year after birth, when it begins to diminish in size, and 

 by the period of puberty has almost entirely disappeared. 

 Each right and left lobe, is composed of lobules disposed in a 

 spiral form round a central cavity, which is called a reservoir. 

 — The lobules are held together by dense cellular tissue, and, 

 the whole gland is surrounded by a coarse cellular capsule. 

 The lobules which make this a conglomerate gland are very 

 numerous, and vary in size from that of the head of a pin to a 

 common pea. In each lobule there is a small cavity or secre- 

 tory cell. Several of these cells open into a small pouch, and 

 this again into the central cavity or reservoir, which is lined by 

 a vascular mucous mennbrane. 



— Each lobe of the gland may be carefully unraveled by 

 removing. the coarse cellular capsule and vessels, and dissecting 

 away the firm cellular tissue that liolds the lobules together ; 

 the reservoir then, which in its natural state is folded in a 

 serpentine manner upon itself, may be" drawn out into a length- 

 ened tubular cord, around which the lobules are clustered in 

 a spiral manner, and resemble knots upon a cord, or a string 

 of beads. The reservoir, pouches, and cells, contain a white 

 fluid like chyle or cream, with a small admixture of red 

 globules. The use of this gland is not known. Sir A. Cooper, 

 is disposed to believe, in common with several of the older writers, 

 that the gland is designed to prepare a fluid from the blood of 

 the mother, well fitted for the growth and nourishment of the 

 foetus before its birth, and consequently, before chyle is formed 

 by it from food ; this process continuing for a short time after 



