74 ON THE SUPRA-RENAL, THYMUS, AND THYROID BODIES. 



centres of origin and of nutrition, each for its own group. 

 The mass of the organ is supplied with blood-vessels to convey 

 the blood to and from the part, and with lymphatics which 

 receive the product of solution of the cells, and convey it 

 back again into the general circulation, whence it was origin- 

 ally derived. 



The account of the structure of the thymus given by Sir 

 Astley Cooper is so far incorrect, as this organ contains no 

 reservoirs or cavities in its substance. The cavities exhibited 

 by Sir Astley Cooper in his drawings and preparations are 

 the results of modes of preparing. They are artificial cavities 

 formed by distension, between the somewhat smooth, highly 

 vascular, and slightly adhering outer surfaces of contiguous 

 lobules ; the whole organ being at the same time bound 

 together by a stronger external areolar texture. No milky 

 fluid is found naturally in these interlobular spaces. Indeed, 

 Sir Astley Cooper says, that " the best mode of obtaining it is 

 by cutting the gland into very small pieces and placing them 

 upon gauze, which being squeezed, the solid is separated from 

 the fluid part, and the latter escapes through the gauze." 



The thymus, from the time it assumes its most perfect 

 structure till it begins to degenerate into fatty substance, con- 

 sists of lobes connected by areolar fibres, without cavities or 

 ducts, formed of nucleated cells grouped around germinal 

 spots, deriving matter for the formation of their cells from 

 arteries passing into it, and being relieved of its venous blood 

 by returning veins, being plentifully supplied with lymphatics, 

 which do not communicate with the supposed reservoirs, as 

 has been suggested, but appear to take their origin, as in other 

 parts, by intercellular lacunae, in which the walls seem gradu- 

 ally to lose themselves, as the ducts of the liver are lost 

 among the secreting cells of that organ. 



The thyroid body possesses a structure which is essentially 

 the same as that of the thymus. It differs from the thymus 



