CHAPTER XIII. 



THE BLOOD. 



BY ALEXANDER ROLLETT. 



THE red blood of vertebrate animals consists in part of a solu- 

 tion of various substances the blood plasma and in part of 

 very small corpuscular structures of peculiar form. 



The corpuscles are so abundant and so equally distributed 

 through the fluid medium, that their interspaces are of micro- 

 scopic dimensions, and fresh blood consequently presents to the 

 naked eye the appearance of a homogeneous red fluid. The 

 individual corpuscles do not all agree with one another in their 

 characters, and hence several different kinds may be distin- 

 guished amongst them. 



In the first place, we may distinguish between the coloured 

 and the colourless forms, the number of the former predomi- 

 nating in healthy blood. 



The coloured corpuscles are more uniform than the colourless, 

 amongst which several subdivisions must be made. 



THE BLOOD PLASMA. The blood plasma, or Liguor Sangui- 

 nis, when examined in the fresh state and in microscopically 

 thin layers, is destitute of colour. If a drop of blood be re- 

 moved for a short time from the living body of an animal, 

 fibrin separates from it in a solid form. But in reference to the 

 coagulation of the blood,* we shall here only discuss the micro- 

 scopic phenomena presented by the fibrinous clot. The fibrin, 

 when in small quantities, separates itself in the form of delicate 

 fibres decussating at various angles, though when in large only 



* Compare Kiihne, Lehrbuch der Physiologischen Chemie. Leipzig, 1866, 

 pp. 162 to 174. 



