142 ORGANS OF RESPIRATION. 



At birth, it is much larger, not relatively, but actually, than 

 it is in the adult, and extends from the body of the heart up to 

 the thyroid gland. It is of a very soft consistence and of a 

 pink colour. It is surrounded by a capsule of cellular sub- 

 stance, which, when removed, permits the gland to be resolved 

 into two lobes, one on either side, which adhere to each other. 

 These lobes may be separated with facility into lobules, and 

 contain a whitish fluid. 



A good Essay on the structure of this gland, has latterly been 

 published by the distinguished British surgeon and anatomist, 

 Sir Astley Cooper,* illustrated by excellent plates. From this 

 it appears that the lobules of the gland are formed of vesicles 

 of various sizes, all discharging into a duct which runs from 

 one end of the gland to the other, the consistence of which 

 duct is extremely feeble. This duct and the vesicles may be 

 filled with an injection, by means of a pipe introduced into the 

 substance of the gland. A large lymphatic trunk passes from 

 the gland, on each side, into the transverse vein. 



Sir Astley thinks, or, rather, asks, whether this gland does 

 not prepare a fluid for fnptnl nnurlehmont, m fh^ absence of 

 proper chylification, during foetal life? inasmuch as all the ele- 

 ments of the blood are upon chemical analysis, found in the 

 fluid contained in its cavities. 



It is visible in the third month of gestation, and continues to 

 grow till the end of the second year of extra-uterine life. It 

 then collapses, and its structure is effaced about the twelfth 

 year; its remains are scarcely distinguishable subsequently 

 from the surrounding cellular substance. No excretory duct 

 has been found for it, unless we may consider as such the lym- 

 phatic trunk alluded to by Sir Astley Cooper. Though it 

 clearly belongs to foetal and infantile existence, its use is pro- 

 blematical. The probability is, that it is a diverticulum of 

 blood from the lungs during their state of quiescence in foetal 

 life, and until their structure becomes confirmed and propor- 

 tionately evolved. 



* London, 1832, 



