OF THE THYMUS GLAND. 263 



changes happen, may vary occasionally, and it is probable that 

 they do so in some degree in almost every individual. But I 

 have never seen an instance of the thymus continuing till the 

 time of puberty (cxxvin). These changes in the thymus are 

 not confined to the human body. The same generally take 

 place in all quadrupeds. The thymus of a calf, called by 

 butchers the neck sweetbread, is not found in the bullock of 

 eight years old; at that age it is entirely wasted, and the 

 same change obtains in every other quadruped that I have had 

 an opportunity of examining. 



SECT. 42. The inference naturally drawn from these expe- 

 riments is, that the thymus is necessary to perform an office 

 requisite in the foetus-state, and in the early part of life de- 

 pending upon respiration. 



What this office is, we shall hereafter endeavour more fully 

 to explain (cxxix). 



(cxxvin.) It is now well known that the thymus is occasionally 

 found in adults, examples of which are quoted from various authors by 

 Mr. Simon. a I examined it from a woman aged 25, and found that it 

 contained only a trace of the fluid so abundant in the gland when its 

 functions are active. The thymus, as mentioned in Note cxxvu, is 

 larger after than before birth in healthy animals ; and probably also in 

 the human subject, though this point requires further observations on 

 children who have died suddenly. On the development of the thymus 

 Mr. Simon has given copious details. 



(cxxix.) See Sections 91-94, and Notes cxxvn, CXLIV. 



a Physiol. Essay on the Thymus Gland, pp. 28, 31, 32, 4to, Lond. 1845. 



