HUMAN BLOOD-COEPUSCLES. 15 



LESSON III. 



ACTION OF REAGENTS UPON THE HUMAN BLOOD- 

 CORPUSCLES. 



1. MAKE a preparation of blood as in Lesson II. 1, and apply a drop of water 

 at one edge of the cover-glass. Examine at a place where the two fluids are 

 becoming mixed. Notice particularly the first effect of water upon both red 

 and white corpuscles, as well as the ultimate action. 



Sketch both kinds of corpuscles under the action of water. 



2. Eepeat on another preparation, using very dilute alkali (0'2 per cent, 

 potash in salt solution) instead of water. Notice the complete solution first 

 of the white and then of the coloured corpuscles as the alkali reaches them. 



3. Eepeat on another preparation, using dilute acetic acid (1 per cent.). 

 Observe that the effect of the acid upon the coloured corpuscles is similar to 

 that of water, but that it has a different action upon the colourless corpuscles. 



Sketch two or three of the latter after the action is completed. 



4. Make a preparation of blood mixed with salt solution as in Lesson II. 2, 

 and investigate the action of tannic acid (1 part tannic acid to 1000 of dis- 

 tilled water) in the same way. 



Sketch two or three coloured corpuscles after the reaction is complete. 



The action of reagents upon the human red blood-corpuscles shows 

 that, although to all appearance homogeneous, they in reality consist 

 of an external envelope of colourless material a & <* <l e 

 which forms a thin film enclosing the dis- 

 solved colouring matter or Ticemoglobin. Thus, 

 when water reaches the corpuscle, it passes 

 through the film by osmosis and swells the 

 corpuscle, causing it to become globular ; FlG 14 



eventually the film is burst through, and the a . c> successive effects of water upon 

 colouring matter escapes into the serum. LiutnXsaiV; i SKt $ 

 Salt, on the other hand, by increasing the tannicacid - 

 density of the fluid in which the corpuscles float, causes a diffusion of 

 water out of the corpuscle, and a consequent shrinking and corrugation 

 of the surface, the crenated form (fig. 8, c ; fig. 1 4, /) being thereby 

 produced. The separation of the haemoglobin from the corpuscle can 

 be effected not only by water (fig. 14, a-e), but also by dilute acids, by 

 the action of heat (60 C.), the freezing and thawing of blood, the 

 vapour of chloroform, and the passage of electric shocks through 



