330 THE DUCTLESS GLANDS. 



amount of 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 pro- 

 portionate size and apparent activity of function. The spleen 

 more nearly retains its proportionate size, and enlarges nearly 

 as the whole body does. 



The function of the vascular glands seems not essential to 

 life, at least not in the adult. The thymus wastes and dis- 

 appears ; no signs of illness attend some of the diseases which 

 wholly destroy the structure of the thyroid gland ; and the 

 spleen has been often removed in animals, and in a few in- 

 stances in men, without any evident ill-consequence. It is 

 possible that, in such cases, some compensation for the loss of 

 one of the organs may be afforded by an increased activity of 

 function in those that remain. The experiment, to be com- 

 plete, should include the removal of all these organs, an opera 

 tion of course not possible without immediate danger to life. 

 Nor, indeed, would this be certainly sufficient, since there is 

 reason to suppose that the duties of the spleen, after its re- 

 moval, might be performed by lymphatic glands, between 

 whose structure and that of the vascular glands there is much 

 resemblance, and which, it is said, have been found peculiarly 

 enlarged when the spleen has been removed (Meyer). 



Although the functions of all the vascular glands may be 

 similar, in so far as they may all alike serve for the elabora- 

 tion and maintenance of the blood, yet each of them probably 

 discharges a peculiar office, in relation either to the whole 

 economy, or to that of some other organ. Respecting the 

 special office of the thyroid gland, nothing reasonable can be 

 suggested ; nor is there any certain evidence concerning that 

 of the supra-renal capsules. 1 Respecting the thymus gland, 

 the observations of Mr. Simon, confirmed by those of Friedle- 

 ben and others, have shown that in the hibernating animals, 

 in which it exists throughout life, as each successive period of 

 hibernation approaches, the thymus greatly enlarges and be- 

 comes laden with fat, which accumulates in it and in fat- 

 glands connected with it, in even larger proportions than it 

 does in the ordinary seats of adipose tissue. Hence it appears 



1 Mr. J. Hutchinson, and more recently, Dr. Wilks, following out 

 Dr. Addison's discovery, have, by the collection of a large and valua- 

 ble series of cases in which the supra-renal capsules were diseased, 

 demonstrated most sati>f'actorily the very close relation subsisting be- 

 tween disease of these organs and brown discoloration of the skin; 

 but the explanation of this relation is still involved in obscurity, and 

 consequently does not aid much in determining the functions of the 

 supra-renal capsules. 



