268 



THE MICROSCOPE AND ITS REVELATIONS. 



are of two kinds; the 'red,' and the ' white' or ' colorless. 7 The red 

 present, in every instance, the form of a flattened disk, which is circular 

 in Man and most Mammalia (Fig. 456), but is oval in Birds, Reptiles 

 (Fig. 455), and Fishes, as also in a few Mammals (all belonging to the 

 Camel tribe). In the one form, as in the other, these corpuscles seem to 

 be flattened cells, the walls of which, however, are not distinctly differ- 

 entiated from the ground-substance they contain; as appears from the 

 changes of form which they spontaneously undergo when kept by means 

 of a 'warm stage' 1 at a temperature of about 100, and from the effects 

 of pressure in breaking them up. The red corpuscles in the blood of 

 Oviparous Vertebrata are distinguished by the presence of a central spot 

 or nucleus; this is most distinctly brought into view by treating the 

 blood-disks with acetic acid, which causes the nucleus to shrink and be- 

 come more opaque, whilst rendering the remaining portion extremely 

 transparent (Fig. 455, d). By examining unaltered red corpuscles of the 

 Frog or Newt under a sufficiently high magnifying power, the nucleus is 

 seen to be traversed by a network of filaments,, which extends from it 



FIG. 455. 



FIQ. 456. 



Red Corpuscles of Frog's Blood: a a, 

 their flattened face; 6, particle turned 

 nearly edgeways; c, colorless corpuscle ; d, 

 red corpuscles altered by diluted acetic acid. 



Red Corpuscles of Human Blood; 

 represented at a, as they are seen when 

 rather within the focus of the Microscope, 

 and at b as they appear when precisely in 

 the focus. 



throughout the ground-substance of the corpuscle, constituting an intra- 

 collular reticulation. The red corpuscles of the blood of Mammals, how- 

 ever, possess no distinguishable nucleus; the dark spot which is seen in 

 their centre (Fig. 456, b) being merely an effect of refraction, consequent 

 upon the double-concave form of the disk. When these corpuscles are 

 treated with water, so that their form becomes first flat, and then double- 

 convex, the dark spot disappears; whilst, on the other hand, it is made 



1 A very simple mode of applying continued warmth to an object under obser- 

 vation is to lay the slide on a thin plate of brass or tin, about 3 inches longer 

 than the breadth of the stage, and about 2 inches broad; which must be perfor- 

 ated with a hole about 14th inch in diameter, at the distance of half the breadth 

 of the stage from one end of it. When this plate is laid on the stage, and its hole 

 is brought into the optic axis, so as to allow the light reflected upwards from the 

 mirror to pass to the slide laid upon it, the plate will project about 3 inches on 

 one side of the stage, preferably the right. By placing a small lamp beneath 

 this projection and keeping the finger of the left hand on the part of the plate 

 close to the object (so as to feel the degree of warmth imparted to it), the heat 

 given by the lamp may be regulated by varying its position. -For more exact and 

 continuous regulation of the temperature, recourse may be had to the ' warm 

 stage' devised by Prof. Schafer and made by Mr. Casella, which is traversed by a 



t on7 arm water> See "Q uart - Journ. of Microsc, Sci.," N.S., Vol. xiv. 

 p. o94. 



