III.] HUMAN BLOOD. I I/ 



corpuscles are not of absolutely the same size. This variation in 

 size becomes more marked in some diseases. 



2. Colourless Corpuscles. With a little care in observing, 

 especially when the red corpuscles are in rouleaux, here and there in 

 the field a few colourless corpuscles will be found. They remain 

 isolated and do not form groups. They are few in number, only 

 three to ten being found in one field. The proportion is about 3 to 

 10 per 1000 of red. They are usually spherical, and although they 

 exhibit amoeboid movements at 40 C., at the ordinary temperature 

 they do not do so, and appear as nucleated finely granular masses of 

 protoplasm. They rapidly alter after they are shed. Some of them 

 are larger (o-jVo" inch or 10 /x, in diameter), others smaller than the 

 red corpuscles (fig. 72, L, I). 



Move the cover-glass so as to cause a current in the preparation. 

 Note that the colourless corpuscles adhere to the glass, they are 

 sticky and adhesive, while the coloured ones being smooth, and 

 polished, glide over each other, and frequently impinge on the 

 colourless ones without displacing the latter. 



3. Blood-Plates (see p. 123). 



4. Acetic Acid, Tannic Acid (fig. 66, a, b), Water, Syrup, and 

 Magenta act in great part in the same manner on the coloured and 

 colourless corpuscles of man and mammalia as on the corpuscles of 

 Amphibia. The differences are due to structural differences in the 

 corpuscles. 



Thus in the coloured mammalian corpuscles acetic acid de- 

 colorises them and renders them spherical (but of course no nucleus 

 is revealed), leaving a hull or stroma, almost invisible in the field. 

 Syrup shrivels them, magenta reveals no nucleus, but on the side 

 of some of the corpuscles a little spot may be observed. Bile makes 

 them pale, and finally dissolves them. Water decolorises the red 

 corpuscles, and makes the blood "laky. " 



5. Amoeboid Movements of White Blood-Corpuscles. In order 

 to study these movements in the white blood-corpuscles of man and 

 warm-blooded animals generally, the temperature of the blood must 

 be near the temperature of the body. To keep the preparation 

 warm, some form of warm or hot stage is necessary. 



For the purposes of the student the following simple contrivance 

 is sufficient. Take an oblong copper plate, 76 mm. long, 25 mm. 

 broad, and 1.5 mm. thick, with a rod 100 mm. long projecting from 

 one side of it, as shown in fig. 75. In the centre of the oblong 

 plate of copper is a hole 15 mm. in diameter. Fix the oblong plate 

 to an ordinary glass slide by means of sealing-wax. 



Make a preparation of blood. Take a cover-glass i inch square, 

 and on it place a drop of normal saline .solution, and to the latter 

 add a drop of blood. Mix them. Apply a ^-iiich cover-glass, so as 



