II.] THE BLOOD. log 



may present here and there a reddish tinge. All tire corpuscles 

 are not affected equally or at the same time. The same effects ar& 

 produced by strong saline solutions. 



6. Tannic Acid (H). On a slide mix a drop of blood with a 

 drop of tannic acid, using a relatively large drop of the acid fluid ; 

 wait for about a minute, and then apply a cover-glass. 



(a.) Observe that some of the corpuscles become globular, while 

 the haemoglobin passes out of the corpuscles at one or more spots, 

 and appears on the surface in the form of one or more small 

 granular buds (fig. 66, c). Sometimes the bud or buds are small. 

 At others the bud may be as large as the remainder of the corpuscle, 

 which has become smaller and partly decolorised. In other cases 

 it may be collected around the nucleus (Robert*). The tannic acid 

 causes a separation of the haemoglobin from the stroma. 



The solution of tannic acid is made by dissolving 2 grains of 

 tannic acid in i oz. of boiling water, and allowing it to cool. 



FlQ. 66. Actio-i of Tannic Acid 



FIG - 6 7 .-Action of Boracic Acid on a Frog's 

 Red Blood-Corpuscle. 



7. Boracic Acid. Mix a drop of newt's or salamander's blood 

 with a 2 per cent, solution of boracic acid, which takes a short 

 time to act on the corpuscles and produce its effects. 



(a.) Observe that the haemoglobin is collected around the nucleus, 

 so that the presence of the latter is obscured, but in many of the 

 corpuscles fine threads of haemoglobin remain attached to the 

 circumference of the corpuscle, so that the retracted haemoglobin 

 may have a stellate form, while the rest of the corpuscle is colour- 

 less. To the latter Briicke gave the name Oikoid, to the former 

 Zooid (fig. 67). 



If these corpuscles are acted on for twenty-four hours with i per 

 cent, osmic acid, they are " fixed," and may be mounted permanently 

 in glycerine-jelly. 



8. Magenta. Mix a drop of blood and a drop of the special 

 magenta fluid (p. 74) on a slide, cover, and examine. 



(a.) Observe that the nuclei of the corpuscles, both red and 

 white, are stained of a brilliant red, although the surrounding part 

 of the corpuscle is not so stained, unless the magenta be in great 

 excess. All the corpuscles are not stained equally brightly. On 

 the edge of some of the corpuscles at one or more points will be 

 found small coloured spots or thickenings. 



