.34 PROPERTIES OF LIQUOR SANGUINIS. FIBRIN. [BOOK I. 



The specific gravity of plasma doubtless differs imperceptibly 

 from that of the serum which separates from it, and which in the 

 case of man varies between 1026 and 1029. It is stated by Gautier 

 that the density of human plasma varies between 1027 and 1028, 

 though no authority for the statement is given 1 . 



The reaction of the plasma is, like that of the blood, and of the 

 serum which separates from it after coagulation, alkaline. 



The coagulation of the liquor sanguinis, which may be readily 

 watched by allowing the temperature of the fluid separated from 

 horse's blood at C. to rise slightly, follows exactly the same course 

 as the coagulation of the blood. The process commences on the 

 surface and sides of the liquid and then extends throughout the whole 

 mass, which assumes the appearance of a colourless trembling jelly ; 

 the surface of this jelly is from the first seen to be somewhat 

 depressed, and from it there exude droplets of clear serum. After 

 some hours the coagulum is found to have contracted and floats 

 in serum exactly as does a blood clot under similar circumstances; in 

 the case of the coagulation of plasma, however, the coagulum, as it does 

 not entangle blood corpuscles, is colourless and comparatively small. 



The serum is found to be more alkaline than the plasma from 

 which it has separated. 



The plasma, it has already been remarked, differs from the serum 

 in its containing the body or bodies which, separating from it, form 

 fibrin. It will be convenient therefore to examine first of all the 

 properties of fibrin and then to consider the facts which relate to 

 the assumed precursors of fibrin in the plasma. 



Fibrin. 



Micro- When a drop of freshly drawn blood is examined under 



scopic ob- the microscope in the usual way, filaments are often ob- 



onThe OI served to stretch across the preparation ; these are usually 



character on ty se en under tolerably high powers and by careful focus- 



and ar- ing ; the filaments consist of the newly formed fibrin. If 



range- a pretty thick stratum of frog's blood be mounted for 



JS?*? f microscopic examination in the usual way, the edges of the 

 Fibrin in . r , . , . . . d __ J > 



blood clot, preparation being touched with paraffin to prevent evapo- 

 ration, after some hours the coloured corpuscles are seen 

 to have arranged themselves into patches, the corpuscles in each 

 patch appearing to radiate from a centre, at which are seen minute 

 granulations. Under a sufficiently high power each individual blood 

 corpuscle is seen to have assumed a pear shape. The appearances 

 alluded to, which have been admirably described by Ranvier 2 , are 

 due to the contraction of filaments of fibrin, which have the afore- 

 mentioned granulations for their centre. The actual arrangement of 



1 Gautier, Chimie applique'e a la Physiologic, 1874, Vol. i., p. 489. 



2 Ranvier, Traite technique d'Histologie, p. 214 et seq. 



