10 ORGANISED FLUIDS. 



meshes of the cellular tissue which forms the foundation of 

 the substance of the gland itself. 



Now it is impossible to conceive that solid organisms of such 

 a size as the corpuscles of the thymus can enter the lymphatics 

 bodily : if they are received into the circulation at all, they 

 must first undergo a disintegration and dissolution of their 

 structure. 



Both Mr. Gulliver and Mr 4 Simon * regard the corpuscles 

 of the thymus as cytoblasts ; the former, however, believes 

 that before their development as cytoblasts they enter the 

 circulation, while the other conceives that they are developed 

 in the gland itself into true nucleated cells. 



It is difficult to suppose with Mr. Simon, that the small 

 and uniform granular corpuscles of the thymus are developed 

 into the large, complex, and curiously constituted true 

 secreting cells of that gland. 



Whether this be the case or not, however, it would appear 

 that Mr. Simon has fallen into a certain amount of error in 

 his account of the structure of the thymus gland, and also of 

 other analogous glands, as well as in the generalisations 

 deduced by him therefrom. 



Thus Mr. Simon states, that in early life there exists in the 

 thymus gland " no trace whatever of complete cells ; " that it 

 is only in later life that nucleated cells are formed, and that 

 these are developed out of the granular corpuscles already 

 referred to, and which are alone present in the gland in 

 the first years of its existence. The same statements are 

 applied to the thyroid body. 



But Mr. Simon does not rest here : he regards the long 

 persistence of the corpuscles, which he states are to be found 

 in all those glands which secrete into closed cavities, in the 

 condition of cytoblasts, as constituting a remarkable and 

 important distinction between the glands in question and the 

 true secreting glands which are furnished with excretory ducts. 



These observations are to a considerable extent erroneous, 

 as is proved by the fact that true nucleated cells are to be met 



* Prize Essay on the Thymus Gland. London, 4to, 1846. 



