CONVERSION OF CHEMICAL ENERGY 



79 



they become hard and rigid. These changes are reversed by 

 transferring the potato strips from one solution to the other. 



The first quantitative investigations of these phenomena 

 were carried out by de Vries, who determined the strengths of 

 solutions which just failed to produce plasmolysis. * 



Hamburger made corresponding observations on red blood 

 corpuscles,| but as there is no rigid cell wall changes in volume 

 were observed and not plasmolysis. Under certain conditions 

 (usually preceded by swelling of the corpuscles), the 

 haemoglobin escapes from the corpuscles ; the bright red 

 opaque suspension of corpuscles becomes a dark red trans- 

 parent solution of haemoglobin and the framework of the 

 corpuscles (stroma) remains as semi-opaque bodies called 

 ghosts. This process is called laking or haemolysis. 



By comparing the concentrations of solutions that just 

 failed to produce haemolysis and those that maintained the red 

 blood corpuscles at the same volume that they occupy in the 

 blood, it has been found that in many cases these concen- 

 trations are such that they all possess the same osmotic con- 

 centration. In other words the effects on the cells correspond 

 to measurements of osmotic pressure as made by freezing 

 point or other determinations. 



TABLE XVI 



Showing the strengths of solutions that cause hczmolysis of red 

 blood corpuscles. 



Calculated from figures given in Landolt and Bernstein, 

 f Using the figures for the dissociation of sodium acetate, 

 j Assuming the same extent of dissociation as in potassium sulphate. 



In the preceding table it is seen that certain substances 

 seem to act by a purely physico-chemical osmotic effect. 

 There are, however, substances such as urea and ammonium 



* H. de Vries, Jahrbuch wiss. Bot., 1884, vol. 14, p. 427. 

 t H. J. Hamburger, Arch. f. Physiol., 1886, p. 476. 

 J Modified from H. J. Hamburger, Osmotischer Druck und lonenlehre, 

 Wiesbaden, 1903, vol. I, p. 165. 



