26 . MICROSCOPICAL DIAGNOSIS. 



Examined with a magnifying power of about four hundred 

 diameters one never fails ; when the specimen is prepared as 

 described above to see beautiful and perfect representations of the 

 rouleaux. 



Nearly all the red corpuscles are seen adhering to each other by 

 their flat sides. The rouleaux can be broken and the corpuscles 

 separated from each other by gently tapping the edge of the cover- 

 glass. Not all the red corpuscles necessarily enter into the rouleaux, 

 yet the white never do, therefore when examining a specimen of 

 blood, showing the rouleaux, a few corpuscles will be seen alone* 

 larger in size than the mass of corpuscles, globular and granular, 



Fig. 8. 



A, human blood in rouleaux, a, white corpuscles, x 400. B, human red blood corpuscles, 

 a, seen on edge, b, white corpuscle, x 1000. 



these will be the white corpuscles, or leucocytes. The beginner is 

 frequently troubled to find the white corpuscles of the blood. He 

 should, first, become familiar with the appearance of these bodies 

 by studying them apart from the red corpuscles. This can be done 

 very easily, in a specimen prepared as above, by placing a drop of 

 water to one edge of the cover and a strip of blotting paper at the 

 opposite edge. In this manner all the red corpuscles can be 

 washed away while the white will remain. 



Another method is this, while looking at the red corpuscles 

 they are thrown slightly out of focus by the fine abjustment. If any 

 white corpuscles are in the field they will appear as bright dots; 

 fixing the eye on one of these bright dots the fed corpuscles are 

 refocused when the bright spots appear as white corpuscles. 



Besides the plan described above for obtaining a thin layer of 

 blood the following may be tried: Draw the end of a smooth, 

 ground glass slide through the drop of the blood on the end of the 



