HISTOLOGICAL DEMONSTRATIONS. 61 



83 A. Effect of Gases. The influence of a stream of carbonic 

 acid upon the coloured corpuscles may be studied by Strieker's method. 

 A drop of water is placed on the floor of the chamber in his hot stage 

 (Fig. 48), and a cover-glass, on which a drop of newt's blood has been 

 previously placed, is inverted over the chamber. A ring of oil is 

 painted round the margin of the cover to prevent evaporation. The 

 stage is then gently heated until the water in its moist chamber evapo- 

 rates, and the corpuscles at the periphery of the drop become affected 

 by the moisture. When the red corpuscles are just about to lose their 

 colour, the further addition of heat is discontinued, and a stream of 

 carbonic acid is driven through the chamber by the apparatus described 

 in 258 (Fig. 46). If the coloured corpuscles have been sufficiently 

 acted on by water, the carbonic acid produces a cloudiness within 

 them, which, according to Schmidt and others, is due to the precipi- 

 tation of paraglobulin. The precipitate disappears if a stream of 

 oxygen or common air be substituted for the carbonic acid. 



836. Effect of Electricity. Make a preparation of human 

 blood on a slide with gold leaf electrodes (Fig. 51), and transmit shocks 

 through it from a Du Bois Reymond's induction apparatus, in connection 

 with a voltaic cell as powerful as a small Grove's element. The second- 

 ary should be pushed close up over the primary coil of the apparatus. 

 The electricity causes the white corpuscles to withdraw their processes, 

 and to become more or less globular. The coloured corpuscles become 

 successively crenated, globular, and finally colourless, owing to a diffu- 

 sion of their pigment into the surrounding stroma. A similar effect is 

 produced by discharges from a Leyden jar. These effects, first shown 

 by Rollett and Neumann, are not entirely explained, but in all proba- 

 bility they chiefly result from electrolysis ; although induced is not 

 nearly so powerful as voltaic electricity in giving rise to electrolytic 

 effects. 



830. Inclusion of Solid Particles by the Colourless 

 Corpuscles. As in the case of an amoeba, a white blood corpuscle 

 can entangle and envelope solid particles. This is effected by protru- 

 sions of the protoplasm growing around the particles. To demonstrate 

 this phenomenon, human or newt's blood may be employed ; the latter 

 is, however, to be preferred, on account of the larger size and greater 

 number of the white corpuscles. Fine granules of carmine, vermilion, 

 indigo, or aniline blue that has been precipitated by alcohol from a 

 watery solution, may be employed. (Schultze, Schultzts Archiv, vol. 

 i. p. I.) These substances are reduced to a very fine state of division, 

 mixed with aqueous humour, and introduced into the blood, which may 

 be previously diluted with an equal bulk of aqueous humour. In the 

 absence of aqueous humour, dilute albumin (white of egg I part, | 

 per cent salt solution 2 parts, strained through muslin) may be em- 

 ployed. The blood with the pigment is placed on a slide and covered. 

 Evaporation is prevented by a ring of oil painted round the cover- 

 glass, and the preparation is kept on the warm stage (Fig. 49), at 30 

 C. in the case of newt's blood, and at 38 C. if the blood be human. 



