< MAI'. IV 



I HI. BLOOD 



27 



a-* they air carried by the currents against one another, and, 

 being clastic, immediately resume again their previous form. On 

 iint of these properties they can be forced through spaces 

 which are smaller than their usual diameter. The clastic 

 substance of which they consist, called stroma, is of a close- 

 set, spongy structure, 

 and holds the red colour- 

 ing matter which iscalled 

 'oxyhaemoglobin. The 

 oxyh;unoglobin can be 

 dissolved out of the cor- 

 puscles, and the stroma 

 is then left as a colour- 

 li^s framework. If blood 

 is diluted with water, the 

 stroma takes up more 

 and more water, till the 

 corpuscle swells out and 

 becomes spherical. I f 

 salt is added to the drop 

 of blood, water passes 

 out of the meshes of the 

 stroma, and the corpuscle 

 becomes shrunken and 

 wrinkled. 



The Colourless Corpuscles. The colourless cor- 

 puscles, unlike the red corpuscles, vary much in size, but 

 most of them arc larger than the red, being about TjsVo** 1 of an 

 inch in diameter; some are as small as, or even smaller than, 

 the red. They must be looked for carefully, since they are devoid 

 of colour and scanty. Some are globular in shape, and are 

 crowded with granules ; others are very irregular in outline, and 

 are constantly changing their shape so long as they arc alive. 

 They remain alive for a short time in a drop of blood on a slip 

 of glass, and are active in changing their shape, especially if 

 the glass is kept just warm. The red corpuscles only change 

 tlu-ir shape- through pressure on them, as they are forced against 

 obstacles by the blood stream. The colourless ones, on the 

 other hand, aiv ;u tivr of themselves, and, being more adhr-ivr 

 than the red, are often seen fixed in one spot, changing their 



FIG. 6. Blood corpuscles. 



r, red corpuscles seen on the flat ; r, red corpuscles 

 seen on edge, and run together into rows ; a, 

 f>, colourless corpuscles, nucleus not seen ; c, 

 if, e, colourless corpuscles, nucleus seen ; f, 

 containing also granules. 



