HO PRACTICAL HISTOLOGY. [ll. 



9. Osmic- Acid and Picrocarmine (H). This preparation is 

 best made by mixing a few drops of blood with an equal volume of 

 i per cent, osmic acid in a small tightly-corked tube, or by exposing 

 a thin film of blood to the vapour of a 2 per cent, solution of osmic 

 acid. After two to four hours pour off the supernatant fluid and 

 cover the residue of corpuscles with picrocarmine. After twenty- 

 four hours the picrocarmine can be poured off, and a little of the 

 deposit placed on a slide and mixed with glycerine-jelly dissolved 

 by heat, and covered (p. 85). 



(a.) Observe that the nuclei of the corpuscles are bright-red, and 

 the perinuclear part of the corpuscles yellow. Within the granular- 

 looking nucleus, with a. good lens, may be seen a network of fibrils. 



This preparation is permanent, and must be sealed up or " ringed " 

 after the manner described at p. 88. 



10. Blood of Bird (H). Mount a drop of fresh blood. 



(a.) Observe the red corpuscles, which are elliptical, biconvex, 

 nucleated bodies, but smaller in size and more ^pointed than 

 amphibian corpuscles (fig. 68). 



These corpuscles behave towards reagents as those of amphibians. 



11. Blood of Fish (H). Mount a drop of fresh blood, which is 

 readily obtained from a gold-fish or salmon, but the blood coagulates 

 rapidly. 



J2.) Observe the red corpuscles, which are elliptical, biconvex, 

 nucleated, but the ends are not so pointed as in the bird, while, 



like the bird's corpuscles, 

 they are smaller than 

 those of amphibians (fig. 

 68, F). The blood must 

 be quite fresh. 



In both cases a few 

 colourless corpuscles may 

 be noticed. 



FIG. 68.-Red Blood-Corpuscles of Fish (F) and ( B .-) T ke White C r ~ 



Bird (B), x 45 o. puscles of the Frog or 



Newt. 



12. White Corpuscles. In a fresh preparation of blood (taking 

 care to place a hair under the cover-glass) search for the colourless 

 corpuscles, of which there are several varieties. They are much 

 less numerous than the red. 



(a.) Observe that there is: (i.) The finely granular form, con- 

 sisting of a nucleated mass of protoplasm larger than a red corpuscle 

 (fig. 6 1, m). (ii.) The coarsely granular variety may be found. In 

 it the granules are large and refractive, and often lying at one side 

 of the corpuscles, (iii.) A third variety, much smaller than the 

 others, may be found (iig. 61, k). 



