PHYSIOLOGY. 



PART I.-BLOOD, CIRCULATION, RESPIRATION, AND 

 ANIMAL HEAT, 



BY DR. BURDON-SANDERSOK 



CHAPTER XV. 



THE BLOOD. 

 SECTION I. THE LIQUOR SANGUINIS, OR PLASMA. 



THE blood is not a liquid, in the strict sense, but consists 

 of colored and colorless corpuscles suspended in liquor san- 

 guinis. It is necessary, in order to examine the liquor san- 

 guiuis, to separate the corpuscles from it by mechanical meth- 

 ods i. e., by subsidence and clecantation, or filtration. As, 

 however, it is not possible, under ordinary circumstances, to 

 remove blood from the body without its undergoing that re- 

 markable change which we call coagulation, neither of these 

 methods can be applied to the blood unless by some means or 

 other it can be kept in a fluid state during the process of fil- 

 tration. The earliest successful attempt to accomplish this 

 was made by Johannes Miiller. His experiment consists in 

 allowing a frog to bleed into a solution of sugar (half per 

 cent.), and then rapidly filtering the mixture. The large cor- 

 puscles of the frog's blood are retained, and the liquid passes 

 transparent, and free from corpuscles. After a time it solidi- 

 fies to a trembling jelly, which eventually contracts into a clot 

 surrounded lr^ serum. This experiment was, for a long period, 

 the only proof of the existence in the blood of a liquid possess- 

 ing the properties of plasma that is, of the fact that the liq- 

 uor sanguinis solidifies when left to itself, quite independently 

 of the corpuscles. It does not, however, enable us to study 

 the properties of this liquid completely, because in Miiller's 

 filtrate it is diluted with saccharine solution. 



