Il] BLOOD COEPUSCLES OF FROG 15 



power. Take a little blood from a freshly killed frog 

 and establish a current underneath the cover-slip from 

 one side of it to the other (cp. 5). The first small 

 drops will have partially clotted and will serve as an 

 imperfect barrier to the corpuscles in the current; in 

 such places note that the shape of the red corpuscles is 

 easily changed and recovered, and that the colourless 

 corpuscles stick to one another and to the glass more 

 than do the red. After the current has passed for a 

 short time largish clumps of colourless corpuscles will 

 be seen. 



8. Evaporate to dryness on a slide a drop of a 

 saturated solution of urea ; on this place a small drop 

 of blood, mount at once, press down the cover-slip, 

 and observe the breaking up of the red corpuscles into 

 spheres ; sometimes a corpuscle will put out a varicose 

 filament which breaks up later into spheres. 



9. Action of boracic acid. Let a little fresh blood of a frog or 

 newt run into about five times its volume of a 2 p.c. aqueous 

 solution of boracic acid, and mount at once a drop of the mixture. 

 The corpuscles, nearly normal in appearance when first mounted, 

 rapidly become altered ; in all or nearly all cases the haemoglobin 

 leaves the stroma or the outer part of it, and becomes accumu- 

 lated around the nucleus. As this is taking place the haemoglobin 

 may form a star-shaped figure in the stroma ; from some cor- 

 puscles, but as a rule, from a few only, the mass formed by the 

 nucleus with the haemoglobin is extruded. 



10. Dilute a little fresh blood with twice its volume of -6 p.c. salt 

 solution ; mount a drop of the mixture and place it aside for an hour 

 or so to clot ; irrigate it with 30 p.c. alcohol and then with Spiller's 

 purple dissolved in water or in dilute alcohol. Note the deeply stained 

 network of fibrin fibrils and the numerous long threads of fibrin 

 running from the broken-down colourless corpuscles. 



