72 HANDBOOK OF PHYSIOLOGY. 



softer mass within; again, if a needle be rapidly drawn across a drop of 

 blood, several corpuscles will be found cut in two, but this is not accom- 

 panied by any escape of cell contents; the two halves, on the contrary, 

 assume a rounded form, proving clearly that the corpuscles are not mere 

 membranous sacs with fluid contents like fat-cells. 



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

 the oval disc-shaped corpuscles become spherical, and gradually discharge 

 their haemoglobin, a pale, transparent stroma being left behind; human 

 red blood-cells change from a discoidal to a spheroidal form, and dis- 

 charge their cell-contents, becoming quite transparent 

 and all but invisible. 



* & ii. S dine solution (dilute) produces no appreciable 



$& effect on the red blood-cells of the frog. In the red 



blood-cells of man the discoid shape is exchanged for a 

 FIG. 67. spherical one, with spinous projections, like a horse- 



chestnut (Fig. 67). Their orginal 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 



FIG. 68. 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 Ion? diameter is here given. It is remarkable, that although the siza 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 great- 

 er, in others much less than the red corpuscles existing side by side with them. 



nucleus becomes strongly granulated, and all the coloring matter seems 

 to be concentrated iu it, the surrounding cell-substance and outline of 



