CHAP, vn BLOOD-CORPUSCLES 105 



eye, they will appear red : they are hence called red 

 corpuscles. Frequently they are seen turned on edge (D), 

 and their appearance in this position shows them to be 

 flat, oval discs with a swelling in the centre. They are 

 about ^th of a millimetre (about y^^th inch) in long 

 diameter. 



Among the red corpuscles are found, in much smaller 

 numbers, bodies not more than half the long diameter of 

 the red corpuscles in size, quite colourless, distinctly 

 granular so as to have the appearance of ground glass 

 and with a slightly irregular outline (Fig. 26, A). 

 These are the colourless corpuscles or leucocytes. They 



D 



FIG. 26. Blood-corpuscles of the Frog. ( x 525.) 



A, colourless corpuscle ; B, the same in process of division ; C. red corpuscle, 

 surface view ; D, the same, edge view. nu. nucleus. (From Parker's Biology.) 



are not flat, like the red corpuscles, but have the form of 

 irregular lumps. 



The plasma, like the leucocytes, is quite colourless, so 

 that the colour of the blood is seen to be due entirely to 

 the large number of red corpuscles it contains. 



If the drop of blood has been prepared and examined 

 under the high power with sufficient rapidity, a remark- 

 able phenomenon can be made out with regard to the 

 colourless corpuscles. This can be most easily demon- 

 strated by making a series of outline sketches of the same 

 leucocyte at intervals of a minute or two. You will then 

 notice that the sketches all differ from one another : in 

 one there will perhaps be a little projection going off to 

 the right ; in the next this will have disappeared and a 

 similar projection will have appeared on the left, and so 



