MICROSCOPICAL DIAGNOSIS. 27 



finger, press the end of this slide against the flat surface of another 

 slide, and draw it quickly across the same, holding the two slides 

 perpendicular to eachother. 



The end of the first slide should be placed a little to the right 

 or left of the centre of the other slide, in order that the middle of 

 the film of blood may be on the middle of the slide. The cover is 

 applied at once and the specimen examined. 



If it be desirable to preserve the specimen, then proceed as just 

 described only do not apply the cover. Then examine the specimen 

 and if found suitable a ring of the white zinc is placed around the 

 most desirable portion. The slide is now gently heated in order to 

 dry the air that is in the cell. The cover is then applied and an- 

 other ring of the white zinc added. 



The red corpuscles appear as circular, flattened, biconcave discs 

 with rounded edges. When seen on the side the centre appears 

 either light or dark, depending upon the focus. Acting as a bicon- 

 cave lens, when the object is slightly within the focus, the centre 

 will appear light, when without the focus dark. The red corpuscles 

 of all the mammalia are of this shape, with one exception, the 

 camelidae, in which they are oval. 



The red-corpuscles have a light amber or yellowish-green color; 

 they are red only when seen in masses. 



The size of the red corpuscle varies, not only in the same in- 

 dividual at different times, but also in the same drop of blood ex- 

 amined at any one time. The size usually give is from -j^g-j to -g^Vo 

 of an inch. 



The following is a list of measurements of the red corpuscles of 

 some of the different animals, as gived by Gulliver: 



Man, 1-3200 



Dog, 1-3542 



Cat, 1-4404 



Hog, i-4 2 3 



Horse, - 1-4600 



Sheep, 1-6355 



Ox, 1-4267 



Musk-deer, - - 1-12325 



(For full table see Sydenham edition of Hewson's works, p. 237, or 

 consult some of the standard works on physiology). The point that is 



