OF THE CAPILLARY VESSKLS. 



sels over the non-injectoble parts. In the same degree as it 

 advances in age, on the contrary, the proportion of non-inject- 

 ahle parts increases, and that of the capillary vessels dimi- 

 nishes. 



385. Beyond the capillary blood vessels of the. diameter 

 of a coloured globule, are there other smaller vessels which 

 afford a passage to the colourless part of the blood? This is a 

 question of very difficult solution. 



Boerhaave, Vieussens, Ferrein, Haller, Soemmering, Bichat, 

 Chaussier, and many modern anatomists and physiologists, 

 admit serous vessels beyond the last blood vessels, and Bleu- 

 land even thinks he has demonstrated their existence. 



On the other hand, Prochaska, Mascagni, Richerand, and 

 several others, are of opinion that there are no vessels of this 

 kind. It is necessary to examine the facts and reasons ad- 

 duced in support ofthe.se opinions. 



386. Edmund King was one of the first who substituted 

 for the hypothesis of the ancients, respecting the existence of 

 a parenchyma in the viscera, that of a purely vascular struc- 

 ture, which supposes that there are serous vessels; for the last 

 capillary blood vessels are far from occupying or forming the 

 whole substance of the tissues. 



Vieussens and Boerhaave especially, have admitted not only 

 one, but several orders of decreasing and colourless vessels. 

 The disciples of Boerhaave, Haller, the most celebrated of 

 them, and most of the physiologists up to the present time, 

 have also admitted serous vessels, forming a continuation of 

 the arteries beyond the point at which the veins begin. They 

 found their opinion upon the microscopical observations of 

 Leuwenhoek, who speaks of vessels admitting only serous 

 globules, upon the phenomena of injection, and particularly 

 on those of inflammations, which renders parts naturally white 

 and transparent, more or less red. 



We may add to this, that red and injectable capillary ves- 

 sels known in certain organs, are in so small a proportion to the 

 non-injectable substance, that it is difficult to conceive how 

 their nutrition could occur without there existing circulating 



