214 



MANUAL OF PHYSIOLOGY. 



PLASMA. 



The fluid part of the blood is of a pale straw-color, when pure 

 and free from the coloring matter of the blood-corpuscles, and of 

 slightly less density than the blood-corpuscles (v. p. 211). Ex- 

 cept special precautions are taken the plasma is altered when 

 removed from the bloodvessels and coagulation of the blood takes 

 place ; so that, under ordinary circumstances, plasma does not 



FIG. 96. 



Rcticulnm of Fibrin Threads after staining has made them visible. The 

 network (6) appears to start from granular centres (a). (Ranvier.) 



come under observation, except when the constitution of the blood 

 is revealed by the microscope. It was first separated from the cor- 

 puscles by the filtration of frog's blood, to which had been added 

 strong syrup, which checks coagulation and spoils the flexibility 

 of the corpuscles, so that they are caught in the meshes of the 

 filter, and the clear plasma passes through. 



To obtain mammalian plasma free from corpuscles it is neces- 

 sary to use some other method, as the small elastic corpuscles 

 easily run through the meshes of the thickest filter-paper. 



