228 OF ABSORPTION AND SANGUIFICATION. 



The large many-nucleated cells (myeloplaxes or giant cells) described by 

 Robin as existing in the medulla of bones, may possibly, as Neumann sur- 

 mises, represent the mother cells of the lymph-corpuscles, or as Bizzozero 

 maintains, such many-nucleated cells with the pigment-granules that are 

 often found in them indicate that destruction as well as development of blood- 

 corpuscles takes place in the medullary tissue of the bones. The whole 

 subject has an important bearing on the Leucaemia, so often associated with 

 disease of osseous tissue. Hosier 1 observes that marked changes occur in 

 the medulla of bones after extirpation of the spleen. 



165. That the Ductless or Vascular Glands, of whose peculiar structure 

 and relations we have thus taken a general survey, have some office of im- 

 portance to perform in the preparation and maintenance of the blood, cannot 

 any longer be reasonably questioned ; and the determination of this point 

 may be fairly regarded as a considerable step in the investigation. It is 

 obviousj from the very copious supply of blood which they receive during 

 the period of their functional vigor, and from the manner in which this is 

 distributed by minute capillary plexuses on the exterior, and even through 

 the interior, of the glandular vesicles, that it must be subservient to some 

 process of active change ; and the aspect of the contents of these vesicles, 

 as well as of the substance in which they are imbedded, indicates that cell- 

 growth is rapidly proceeding, at the expense of the materials thus afforded. 

 But, on the other hand, that the products of this cell-growth are not sub- 

 stances, which, like those of the ordinary glands, must be separated from 

 the blood, either for its purification, or to serve some special purpose in the 

 economy, appears from the fact that they are not carried off by ducts ; but 

 are received again into the current of the circulation. With the exception 

 of the Spleen, all the ductless glands thus discharge 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 pass through the liver before it enters 

 the vena cava. 



166. Whatever materials, then, are withdrawn from the blood by these 

 organs, are returned to it again in an altered state ; and it may fairly be in- 

 ferred from this circumstance, that the change which they have undergone 

 is one that prepares them for higher uses in the economy. 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 luttrttire, i. <-., 

 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 Thyrnus in young animals (and particularly 

 its rapid diminution in overdriven lambs, and its subsequent gradual redis- 

 tension during rest, if plentiful nutriment he afforded), lead to the conclu- 

 sion that such is almost undoubtedly the function of that body. And such 

 would also seem to be the justifiable inference from the researches of Mr. 



1 Ontnilblatt, 1871, p. 290. 



