144 HANDBOOK OF PHYSIOLOGY. 



(fig. 122) represent the successive stages of the change. A similar loss of color 

 occurs in the red cells of human blood, which, however, from the absence of 

 nuclei, seem to disappear entirely. 



iv. Alkalies cause the red blood-cells to swell and finally to disappear. 



v. Chloroform added to the red blood-cells of the frog causes them to part 

 with their haemoglobin ; the stroma of the cells becomes gradually broken up. 

 A similar effect is produced on the human red blood-cell. 



vi. Tannin. 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, project- 

 ing from the free surface (Roberts' macula) : the coloring matter becomes at 

 the same time concentrated in the nucleus, which grows more distinct (fig. 

 123) . A somewhat similar effect is produced on the human red blood corpuscle. 



vii. Magenta, when applied to the red blood-cells of the frog, produces a 

 similar little knob or knobs, at the same time staining the nucleus and causing 

 the discharge of the haemoglobin. The first effect of the magenta is to cause 

 the discharge of the haemoglobin, then the nucleus becomes suddenly stained, 

 and lastly a finely granular matter issues through the wall of the corpuscle, 

 becoming stained by the magenta, and a macula is formed at the point of es- 

 cape. A similar macula is produced in the human red blood-cells. 



viii. Boric acid. A 2 per cent solution applied to nucleated red blood-cells 

 (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 (fig. 124). The result of this experiment led Brticke to distinguish the 



Fig. 122. Fig. 123. Fig. 124. Fig. 125. Fig. 126. 



Effect of acetic acid. Effect of tannin. Effect of boric acid. Effect of gases. Effect of heat. 



colored contents of the cell (zooid) from its colorless stroma (cecoid) . When 

 applied to the non-nucleated mammalian corpuscle its effect merely resembles 

 that of other dilute acids. 



ix. Ammonia. Its effects seem to vary according to the degree of concen- 

 tration. Sometimes the outline of the corpuscles becomes distinctly crenated ; 

 at other times the effect resembles that of boracic acid, while in other cases 

 the edges of the corpuscles begin to break up. 



Gases. Carbonic acid. If the red blood- cells of a frog be first exposed to 

 the action of water- vapor (w r hich renders their outer pellicle more readily per- 

 meable to gases), and then acted on by carbonic acid, the nuclei immediately 

 become clearly defined and strongly granulated ; when air or oxygen is admitted 

 the original appearance is at once restored. The upper and lower cell in fig. 

 125 show the effect of carbonic acid ; the middle one the effect of the re-admis- 

 sion of air. These effects can be reproduced five or six times in succession. 

 If, however, the action of the carbonic acid be much prolonged, the granula- 

 tion of the nucleus becomes permanent ; it appears to depend on a coagulation 

 of the paraglobulin. 



Heat. The effect of heat up to 50 C 60 C. (120140 F.) is to cause the 

 formation of a number of bud-like processes (fig. 126) . 



