CHAPTER XV 



BLOOD AND OTHER CELL MEDIA 



The coagulation of blood is nothing more than a gel formation 

 of a protein hydrosol, the gel being called fibrin and the same 

 substance in colloidal solution, fibrinogen. According to Howell 

 (1914) the fibrin clot is a mass of acicular crystals. This coagu- 

 lation leads to the distinction of plasma, the medium in which the 

 blood corpuscles float, and serum, the same minus the fibrinogen. 



As was previously stated, the permeability of the blood cor- 

 puscles seems to be nearly the same as the permeability of plant 

 cells. Overton claimed plant cells to be impermeable to salts. 

 The same seems to be true of blood corpuscles for otherwise 

 how is the difference between the salts of the plasma and serum 

 maintained since Hober has shown that the ions are not bound 

 but free to move within the corpuscles. Abderhalden gives the 

 following data of the salts of corpuscles and plasma in parts 

 per hundred : 



Notwithstanding this evidence Hamburger claims that the cor- 

 puscles are freely permeable. 



The main difference noted between the permeability of plant 

 cells and blood corpuscles was in case of urea, to which the 

 plant cell is said to be impermeable, whereas some blood cor- 

 puscles, at leasts allow it to pass through. It would be interesting 

 to test the permeability of the erythrocytes of elesmobranchs 

 (sharks and rays) to urea, since its concentration in the blood 

 of these fish is about 5 per cent, whereas it exists only in very 

 small quantities in the blood of other animals. 



