158 THE BLOOD 



The cells in figure 127 represent the successive stages of the change. A 

 similar loss of color occurs in the red cells of human blood, which, from the 

 absence of nuclei, seem to disappear entirely. 



Alkalies. Alkalies cause the red blood corpuscles to absorb water and 

 finally to disintegrate. 



Chloroform and Ether. These reagents when added to the red blood- 

 cells of the frog cause them to part with their hemoglobin; the stroma of the 

 cells becomes gradually broken up. A similar effect is produced on the 

 human red blood-cell. 



Tannin and Boric Acid. When a 2 per cent, fresh solution of tannic acid 

 is applied to frog's blood it causes the appearance of a sharply defined little 

 knob, projecting from the free surface (Roberts' macula}. The coloring 

 matter becomes at the same time concentrated in the nucleus, which grows 

 more distinct, figure 128. A somewhat similar effect is produced on the 

 human red blood corpuscle. 



A 2 per cent, solution of boric acid applied to nucleated red blood-cells of 

 the frog will cause the concentration of all the coloring matter in the nucleus; 

 the colored body thus formed gradually quits its central position, and comes 

 to be partly, sometimes entirely, protruded from the surface of the now 

 colorless cell, figure 129. The result of this experiment led Briicke to dis- 

 tinguish the colored contents of the cell (zoo'id) from its colorless stroma 

 (ecoid). When applied to the non- nucleated mammalian corpuscle its effect 

 merely resembles that of other dilute acids. 



3. Phagocytosis in White Corpuscles. Mix some very fine pigment 

 granules, bacterial emulsion, or charcoal with a few drops of frog's blood, 

 let stand for 10 or 20 minutes, then mount a drop on the glass slide or 

 make a smear and stain and examine under a high- magnifying microscope. 

 Or inject a few drops of one of these pigments suspended in physiological 

 saline and after a few minutes examine drops of the blood as above. In a 

 favorable field here and there will be found some white corpuscles which 

 have taken up the pigment. Colored corpuscles have been observed with 

 fragments of pigment embedded in their substance. White corpuscles 

 have also been seen in diseased states of the body to contain micro-organisms, 

 for example bacilli, and have the power of destroying these organisms, which 

 gives them the name phagocytes. 



4. Enumeration of the Blood Corpuscles. Several methods are 

 employed for counting the blood corpuscles, most of them depending upon 

 the same principle; i.e., the dilution of a minute volume of blood with a 

 given volume of a colorless solution similar in specific gravity to blood plasma, 

 so that the size and shape of the corpuscles are altered as little as possible. 

 A minute quantity of the well-mixed solution is then taken, examined 

 under the microscope, either in a flattened capillary tube (Malassez) or in 

 a cell (Hayem and Nache, Cowers) of known capacity, and the number of 



