12 THE ESSENTIALS OF HISTOLOGY 



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. Repeat 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 (2 per cent, solution) in the same 

 way. 



Sketch two or three coloured corpuscles after the action 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 intimate intermixture of the colour- 



6 c d e ing matter or haemoglobin with certain 

 H ^ (-) other substances (globulin, lecithin, cho 

 lesterin), which are left as the colourless 

 stroma, on dissolving out the haemo- 

 globin, or on causing its discharge by 

 any means from the corpuscle. This 

 1G ' separation of the haemoglobin from the 



a-e, successive effects of water upon a i_ .a? j. j i /.c-i-i 



red corpuscle;/, effects solution of stroma can be effected by water (fig. 11, 



salt; Deflect of tannic acid. a _^ and algo by dilute acidg> by the 



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

 of chloroform, and the passage of electric shocks through blood. 1 



1 In the blood of some animals crystals of haemoglobin readily form after 

 its separation by any of these means from the red corpuscles. These crys- 

 tals are rhombic prisms in most animals, but tetrahedra in the guinea-pig, and 

 hexagonal plates in the squirrel. They are most appropriately studied along 

 with the chemical and physical properties of blood, and are therefore omitted 

 here. The same remark applies to the minute dark-brown rhombic crystals 

 (Jicsinin), which are formed when dried blood is heated with glacial acetic acid, 

 and to the reddish -yellow crystals of hcematoidin, which are found in old blood 

 extravasations. 



