30 MICROSCOPICAL DIAGNOSIS. 



No other conclusion can be reached than that the red 

 corpuscles of the blood of man and the dog are the same in 



size. 



In the case of the five animals, the cat, hog, horse, sheep and 

 ox; the corpuscles of the ox and hog are the nearest in size to those 

 of man; hence if we can tell the blood of these animals from that 

 of man, we shall be able to tell, even more readily, the blood of the 

 cat, horse and "sheep. 



Can the blood of the ox and hog be told from that of man, 

 even when dried or in clots? We believe that a positive distinction 

 is possible, not only in freshly prepared specimens, but also when 

 the specimens have been placed under very unfavorable conditions, 

 as when the blood has been dried upon clothing or pieces of wood, 

 etc. Still the very best of aids should be at the manipulators com- 

 mand. Very high magnifying powers should be used, from three to 

 five thousand diameters, requiring a 1-25 or 1-30 or 1-50 objective. 

 A very accurate cob-web eye-piece micrometer has proved indis- 

 pensable in our hands. The value of the spaces on the milled head 

 should be ascertained by using a stage micrometer known to be 

 accurately ruled. Again, a large number of corpuscles should be 

 measured and their mean average taken. In no part of the general 

 or special work of the microscopist are attention to detail, great 

 care, judgment and skill in such demand. What then shall we say 

 of those who show such a reckless ambition in this particular line? 



If, then, the question be asked us is this the blood of man as 

 distinguished from the blood of all other animals? We should be 

 forced to reply, it is impossible to tell. If, however, the question 

 is to decide between the blood of man and one of the inferior ani- 

 mals, many times a positive a*nswer could be given. 



Between the blood of man and his most constant companion, 

 the dog, there appears to be no difference; while it is possible to tell 

 the difference between the blood of man and the blood of the 

 sheep, cat, horse, hog and ox. 



There is some discussion concerning the best method of exam- 

 ining a specimen of dried blood. We believe the following method 

 will give as good results as any: Some of the dried blood is scraped 

 from the surface to which it is attached, and the dry clot placed on 

 a slide and covered with a thin glass. If the operator should not 

 have thin enough glass to use with his 1-30 or 1-50 he can use, for 

 the time, a thin scale of mica. A drop of saline solution (three- 



