158 ON THE NATTRi: AND PRlNCTrLES OF 



lateral pressure of the blood contained in the 

 of the kidneys operated on is capable of explaining 

 the variety in the effects produced, it is necessary to 

 bear in mind the peculiar physical composition of 

 that fluid while circulating in the vessels of a living 

 animal. For general purposes it is sufficient to con- 

 sider it as consisting of liquor sanguinis and red 

 globules ; but, in connection with the present inquiry, 

 we must scrutinise more closely the composition of 

 the former substance. It is this which gives to the 

 blood all its peculiarities as a fluid ; and in it also 

 resides that self-coagulating power which distin- 

 guishes the vital from every other albuminous so- 

 lution. 



Now the liquor sanguinis, while in its natural 

 state of motion, is, by a very simple process of phy- 

 sical analysis, clearly resolvable into three distinct 

 portions, the constituent particles of which possess 

 very different degrees of cohesive force. We have, 

 first, a serosity or aqueous fluid, holding in solution 

 various saline and animal matters, but no albumen. 

 And, from the great mobility of its particles, this fluid 

 is enabled to permeate with the greatest facility any 

 porous structure ; and is, in fact, naturally filtered 

 through the coats of the Malpighian vessels in the 

 form of urine. 



The next ingredient of the liquor sanguinis is 

 intermediate in its consistency between the aqueous 

 fluid just described, and the still more cohesive self- 

 coagulating albumen or fibrine. It corresponds to 

 the scrum of coagulated blood, and is identical will) 

 the coagulable lymph of old writers : bring neither 



