THE DUCTLESS GLANDS. 417 



nuclei and cells, the materials derived from, the blood are 

 elaborated into a higher condition of organization; and 

 that, when liberated by the dissolution of these cells, they 

 pass into the lymphatics, or are again received into the 

 blood, whose aptness for nutrition they contribute to 

 maintain. 



The opinion that the vascular glands thus serve for the 

 higher organization 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 proportion 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 dis- 

 appears. The thyroid gland and supra-renal capsules, 

 also, though they probably never cease to discharge some 

 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 proportionate size and apparent activity of func- 

 tion. 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 

 disappears ; 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 instances 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 in- 

 creased activity of function in those that remain. The 

 experiment, to be complete, should include the removal of 

 all these organs, an operation of course not possible 



EE 



