II.] 



THE BLOOD. 



107 



elongated, granular-looking included body the nucleus. The long 



axis of the colourless nucleus coincides with the long axis of the 



corpuscle. At first, the nucleus 



may not be very distinct, but 



after a time it becomes distinctly 



visible, and it can be readily 



made so by the action of certain 



reagents, especially weak acids. 



Small vacuoles frequently appear 



in the body of the corpuscle, more 



especially in frogs that have been 



kept some time. In others there 



may be seen a faint radiate 



striping of the corpuscles as if 



there were fine folds in it due to 



partial drying. 



* The yellow colour is due to the 



presence of haemoglobin, which 



is enclosed within, the meshes of 



a colourless stroma or delicate 



framework. 



If the blood be taken from a 

 frog which has been kept through- 

 out the winter, vacuoles may be 

 seen in the hemoglobin of the red corpuscles (fig. 61, v). They are 

 rapidly produced in frogs after the injection of ammonium chloride. 



Sketch two or three corpuscles, both red and white ; the red cor- 

 puscles both on the flat and on edge, and two 

 overlapping each other. 



2. Acetic Acid. To the edge of the 

 cover-glass of the same preparation apply a 

 droj) of dilute acetic acid (i per cent. i cc. 

 glacial acetic acid to 99 cc. of normal saline 

 solution). The acid runs in under the cover- 

 glass, but if it does not, apply a small tri- 

 angular piece of blotting-paper to the opposite 

 edge of the cover-glass. Let one of the angles 

 of the blotting-paper touch the fluid under 

 the cover-glass, and it will suck up some of 

 the blood, and thus cause the acetic acid to 

 run in at the opposite side. This is known 

 as the process of irrigation. Move the slide, and find a part of the 

 object which lias been acted on by the dilute acid. 



(a.) Observe that the red corpuscles, or at least most of them, 

 become spherical and decolorised, the nucleus becomes very distinct 



FIG. 61. Blood of Frog. a. Red corpuscle 

 seen on the flat ; b. In Profile ; c. Three- 

 quarter face ; some of the red corpuscles 

 show the presence of vacuoles (v) ; n. 

 Colourless corpuscle at rest; m. One 

 with amoeboid processes ; p. Fusiform 

 cell, probably from the vascular wall. 



FIG. 62. Amphibian Coloured 

 Blood-Corpuscles seen on 

 the Flat and on Edge, 



X 1000. 



