6t BIOLOGY. [Book I. 



We may view in connection with these substances cholesterine 

 and seroline, formed probably in the nervous tissue. 



All these bodies pass by osmosis through the fine capillary 

 vessels, and sojourn in the blood till they are secreted or excreted 

 therefrom. 



The other azotised substances of the blood belong to the third 

 class of immediate principles. They are the albuminoidal sub- 

 ' stances, properly so called. Urea, creatine, creatinine, and so 

 on, are azotised regressive principles, residua of disassimilation : 

 they form part of the material current coming forth from the 

 organism. On the contrary, the other albuminoidal substances 

 are the residuum of the alimentary elaboration. They are des- 

 tined to repair the waste of the tissues, and form part of the 

 material current entering the economy. 



When the blood of a mammifer is drawn from the vessels, and 

 allowed to rest, it separates into a red clot and a yellowish liquid. 

 The clot is composed of an azotised complex substance, which 

 has been called fihrine, because it has then a fibrillary aspect, and 

 this coagulated substance retains in its meshes the red globules. 

 The ambient liquid contains in solution another azotised sub- 

 stance, denominated albumine, because it has afiinity with the 

 albumen of the egg, though containing a half less sulphur. For 

 a long time there was an erroneous belief that fibrine and albu- 

 mine have as distinct existence in the economy as in the blood 

 when drawn. Fibrine and albuming are, however, isomeric, 

 albumine merely containing a little more water. From important 

 analyses of the blood made by Denis, of Commercy,i it results 

 that in effect the blood contains albumine, which Denis prefers 

 to call serine ; but instead of fibrine there is in the blood another 

 analogous azotised substance, which he calls plasmine. This 

 plasmine, he thinks, evolves itself in the blood when drawn, and 

 thanks to the intervention of the globules, into a coagulable part 

 called /6ri»e, and into another soluble albuminoidal substance, 



' Denis, Corriptes rendus desSiances de VAcadimie des Sciences. 'Paris, 185C 

 and 1858. — Mimovre sur U Sang, Paris, J859, 8vo. 



