THE BLOOD. 



143 



Fluids, i. Water. When water is added gradually to frog's blood, the oval 

 disc-shaped corpuscles become spherical, and gradually discharge their haemo- 

 globin, a pale, transparent stroma being left behind ; human red blood-cells 

 change from a discoidal to a spheroidal form, and discharge 

 their cell- contents, becoming quite transparent and all but in- O #* 



visible. *t 



ii. Saline' solution produces no appreciable effect on the red 

 blood- cells of the frog. In the red blood-cells of man the dis- 

 coid shape is exchanged for a spherical One, with spinous pro- 

 jections, like a horse-chestnut (fig. 120). Their original forms can be at once 

 restored by the use of carbonic acid. 



iii. Acetic acid (dilute) causes the nucleus of the red blood-cells in the frog 

 to become more clearly defined ; if the action is prolonged, the nucleus becomes 

 strongly granulated, and all the coloring matter seems to be concentrated in it, 



Fig. 120. 



Effect cf saline 



solution. 



Fig. 121. The above illustration is somewhat altered from a drawing by Gulliver, in the Proceed. 

 Zool. Society, and exhibits the typical characters of the red blood-cells in the main divisions of the 

 Vertebrata. The fractions are those of an inch, and represent the average diameter. In the case 

 of the oval cells, only the long diameter is here given. It is remarkable, that although the size of 

 the red blood-cells varies so much in the different classes of the vertebrate kingdom, that of the 

 white corpuscles remains comparatively uniform, and thus they are, in some animals, much greater, 

 in others much less than the red corpuscle existing side by side with them. 



the surrounding cell-substance and outline of the cell becoming almost invisi- 

 ble; after a time the cells lose their color altogether. The cells in the figure 



