VASCULAR GLANDS THYROID BODY. 229 



Gray on the Spleen : for the correspondence in the amount of the colorless 

 parenchyma of that organ (and especially of its Malpighian corpuscles) with 

 the general state of nutrition of the animal, its regular increase (in well- 

 fed animals) near the completion of the digestive process, and its gradual 

 diminution in the subsequent interval, seem to indicate that the Spleen, like 

 the Thy m us of the young animal, is a storehouse of nutritive material, which 

 may be drawn upon according to the requirements of the system, just as the 

 fat of the body is a storehouse of combustive substance. And of the exer- 

 tion of an elaborating or assimilative action upon this albuminous matter, 

 during its withdrawal from the current of the circulation in these organs, 

 we seem to have direct evidence, as regards the Spleen, in the large increase 

 of the proportion of fibrin contained in the blood drawn from its veins. It 

 was formerly supposed that the Spleen acted as a kind of reservoir or diver- 

 ticulum for the portal circulation, the vessels of which were thus relieved 

 from undue turgescence, when the alimentary canal was distended with food, 

 and rapid absorption was taking place. Others again were of opinion that 

 a process of disintegration took place in the blood-corpuscles which are found 

 so abundantly in the splenic pulp, but the grounds on which both these 

 views were supported are scarcely tenable in the present state of our knowl- 

 edge. 1 



167. The results then of all the recent investigations on these organs tend 

 to prove that equally with the Absorbent glands, they supply the germs of 

 those cells which are ultimately to become blood-corpuscles. Such, it is well 

 known, was the doctrine of Hewson' 2 in regard to the Spleen and Thymus 

 gland ; and there are many facts which lend it a considerable probability. 

 In the first place, we have seen ( 157, n) that there is no difficulty what- 

 ever in the admission of such corpuscles into the smaller veins of the Spleen, 

 if Mr. Gray's account of its lacuuar circulation, which appears to be fully 

 confirmed by the more recent investigations of Bill roth 3 and Mtiller, 4 be cor- 

 rect ; and that there is no physical impossibility in the reception of particles 

 of such a size into the interior of even 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 ( 142). Secondly, there is an un- 

 usual proportion of colorless corpuscles in the blood of the splenic vein ; so 

 that whilst according to Hirt the proportion of colorless to colored corpus- 

 cles in the blood of the splenic artery is as 1 : 2000, in that of the splenic 

 vein it rises to 1 : 70, and in some diseased conditions it has been known to 

 amount to 1 : 4. 5 Thirdly, if the spleen be extirpated, which has even been 

 performed on man himself, showing that its functions are not indispensable 

 for the preservation of life, the only effects observed have been increase in 

 volume and pigmentation of the lymphatic glands, 6 probably in consequence 

 of their taking on a vicarious action in the development of the white cor- 

 puscles. Fourthly, the period of greatest functional activity of these glands 

 generally, is during the state of early childhood, when the formative pro- 

 cesses are going on with extraordinary activity ; and there is at this time a 



1 See Cycl. of Atiat. and Physiology, vol. iv, p. 796. 



2 See his Third Series of Experimental Inquiries, chaps, iii-v. 



3 Muller's Archiv, 1857, p. 88, and Virchow's Archiv, Bd. xx, p. 410. 



4 See Funke, Physiologic, 1870, p. 241; and Gray, op. cit., p. 148. Dr. Silvester, 

 in an ingeniously written essay (The Discovery of the Nature of the Spleen, 1870), 

 has adduced various arguments against the view that the spleen is a blood-making 

 organ. He regards it as a sanguiferous gland, effecting certain changes in the blood 

 traversing it, and as .the left lateral homologue of a portion of the liver, which is itself 

 a combination of a sanguiferous gland and a biliary apparatus. 



5 Strieker's Manual of Histology, vol. i. 



6 Fahrer and Ludwig, Archiv f. Phys. Heilk., 1855, pp. 315 and 491, and others. 



