272 BLOOD. 



observer distinguishes larger and smaller lymph-granules in the 

 thoracic duct, and is of opinion that the latter only are converted 

 into blood-corpuscles, whilst the larger gradually dissolve in the 

 blood. 



The view that the blood-cells of the embryo originate in the 

 liver, was long since advocated by Reichert,* and recently by 

 several physiologists, and more especially by E. H. Weberf and 

 Kolliker.J Weber showed that in the spring the liver of frogs as- 

 sumes a totally different colour, while at the same season this organ 

 is the seat of an active formation of new blood-cells. Gerlach, 

 whose observations have been supported by those of Schaffner,|| has, 

 however, very recently endeavoured to prove that the spleen is the 

 chief factory for the blood-cells; but the admirable chemical inves- 

 tigations of Scherer seem far more to corroborate the view opposed 

 by Kolliker, and subsequently by Ecker,^[ that the blood-cor- 

 puscles are for the most part destroyed in the spleen. This 

 much, at all events, seems certain, that the formation of the 

 blood corpuscles is not limited to definite organs, for blood- 

 corpuscles appear in the germinal area of the embryo before the 

 formation of vessels and glands. In the area vasculosa, blood- 

 corpuscles and vessels are formed from cells which, according to 

 Reichert, can in no way be distinguished from one another. There 

 can be no doubt, therefore, that the coloured blood- cells may 

 proceed from the colourless ones ; but, as yet, it remains unde- 

 termined whether such is always the order of formation, and how 

 this mode of development is effected. 



If we were to regard the colourless blood- corpuscles as merely 

 a transition stage of formation of the coloured corpuscles, their 

 significance and physiological importance would at once be defined; 

 but however ephemeral their existence in the blood may be, 

 we cannot wholly deny their participation in the chemical meta- 

 morphosis of matter, more especially as many of these bodies do 

 not appear to be converted into coloured corpuscles. They are 

 vital cells, maintaining an active interchange of matter with the 

 blood-plasma, and cannot therefore be wholly without influence on 



* Entwicklungsleben im Wirbelthierreich, S. 22. 



t Zeitschr. f. rat. Med. Bd. 4, S. 160. 



+ Ibid. Vol. 4, pp. 147159. 



Ibid. Vol. 7, pp. 7588. 



|| Ibid. Vol. 7, pp. 345 354. 



f Ibid. Vol. C, pp. 261265. 



