462 OF ABSORPTION AND SANGUIFICATION. 



in the end, were these products discharged (as formerly supposed) by the Lymph- 

 atics; but such an idea is inconsistent with our present knowledge of the 

 distribution of these vessels ; and it may be considered next to certain that the 

 matters, whatever their nature may be, which have been elaborated by these 

 glandular organs, are received again through the capillaries into the Venous 

 system. With the exception of the Spleen, all the ductless glands thus dis- 

 charge their products at once into the general venous circulation ; so that, after 

 having passed through the lungs, they will be carried by the systemic arteries 

 through the system at large : but the splenic vein, it will be remembered, forms 

 one of the roots of the portal trunk, and its blood must thus pass through the 

 liver, before it enters the vena cava. For this exception, a reason may possi- 

 bly be found in one of the offices which has been attributed to the Spleen. 



489. Whatever materials, then, are withdrawn from the Blood by these organs, 

 are returned to it again in an altered state ; and that the change which they have 

 undergone is one that prepares them for higher uses in the economy may fairly 

 be inferred from this circumstance. For, as the blood which has received them 

 is immediately transmitted to the system (except in the case of the splenic blood) 

 without having passed through any other depurating organ than the lungs, it 

 appears fair to conclude that the products which it has taken up in these organs 

 are either combustive or nutritive, i. e. } either serve to maintain the functional 

 activity of the lungs, or of the system, or of the blood itself. Now that they 

 are not destined to prepare a pabulum for respiration appears from the very 

 small quantity of fat which is found in their substance, except when their period 

 of functional activity has gone by. On the other hand, the albuminous nature 

 of the plasma, and the finely-granular appearance which it presents, strongly 

 indicate that a material is here in progress of preparation, which is to be rendered 

 subservient to the formative operations. Various facts which have been noticed 

 in regard to the changes in the bulk of the Thymus in young animals (and par- 

 ticularly its rapid diminution in over-driven lambs, and its subsequent gradual 

 re-distension during rest if plentiful nutriment be afforded), lead to the con- 

 clusion that such is almost undoubtedly the function of that body; and 

 the close resemblance which it bears to the rest in every essential particular, 

 seems to justify our extension of this inference to them. But, further, it does 

 not seem at all unreasonable to suppose that these organs may be concerned, 

 equally with the Absorbent glands, in supplying the germs of those cells which 

 are ultimately to become Blood-corpuscles. Such, it is well known, was the 

 doctrine of Hewson 1 in regard to the Spleen and Thymus gland ; and there are 

 many facts which lend it a considerable probability. In the first place, that 

 there is no physical impossibility in the reception of particles of such a size into 

 the interior of a closed system of capillaries, is proved by the very curious facts 

 already noticed in regard to the passage of starch-grains into the mesenteric veins 

 ( 465). Secondly, many observers have noticed an unusual proportion of color- 

 less corpuscles in the blood of the splenic vein 3 ( 491). Thirdly, the period of 

 greatest functional activity of all these glands is during the state of early child- 

 hood, when the formative processes are going on with extraordinary activity ; 

 and there is at this time a larger proportion of colorless corpuscles in the blood, 

 than at any subsequent period, at least in the healthy state. Further, as Prof. 

 J. H. Bennett has pointed out, the peculiar condition of the blood, which consists 

 in the multiplication of its colorless corpuscles ( 175), is almost always asso- 

 ciated with hypertrophy of one of these bodies; and in one case of this kind, in 

 which the thyroid was the organ affected, its cells and their included nuclei were 



1 See his Third Series of "Experimental Inquiries," Chaps, iii. v. 

 a For one of the most recent and satisfactory testimonies to this fact, see Funke in 

 "Henle's Zeitschrift," 1851, p. 172. 



