28 MICROSCOPICAL DIAGNOSIS. 



of interest in this connection is; what is the value of these corpuscles 

 in medico-legal cases ? That is, by a microscopical examination of 

 a blood-vessel or clot, either fresh or otherwise, can human blood be 

 told from the blood of the lower animals ? This must be considered 

 a very easy matter in some cases. Take, for instance, the red blood 

 corpuscles of all the birds, reptiles, amphibia, and fishes; here the cor- 

 puscles are large, oval bodies, with a large, round or oval nucleus. (The 

 red corpuscles from the family of the lampreys are circular, but the 

 nucleus is prominent.) If, then, the question arises, "Is this human 

 blood," and an examination shows the red corpuscles as oval, nucle- 

 ated bodies, the answer can positively be given, "No." If, how- 

 ever, the corpuscles are circular in shape, having no visible nucleus, 

 then an entirely different problem is involved. Here the question 

 is one of size, and not of shape, and it must be decided by meas- 

 urement. First of all, there must be fixed, if possible, a standard 

 size to the human red corpuscle; for the size of the corpuscles of 

 many of the lower animals is so nearly the same that the figures 

 in each case should give a fixed average size. 



Has the red blood-corpuscle of man a fixed size? It appears 

 not; in fact, by consulting the various authorities, we cannot 

 arrive at a fixed average size. In examining a drop of blood 

 with high powers, one very frequently finds a few minute ' 

 colored corpuscles below the 1-4800 of an inch in 

 diameter. Some few may be found as large as the 

 1-2600 of an inch in diameter. These few, very small and very 

 large, corpuscles are not included in making up the average size; 

 they are easily excluded, and only the most perfect and most com- 

 mon corpuscles are measured. Yet notice what the various author- 

 ities say: 



Diameter of the human red blood-corpuscle as given by 

 Gulliver, 1-3200 of an inch. 

 Flint, 1-3500 of an inch. 

 Dalton, 1-3531 to 1-3050 of an inch. 

 Woodward, 1-3092 of an inch. 

 Frey, 1-2840 to 1-4630 of an inch. 

 Welcker, 1-3230 of an inch. 



Our own observations give 1-3367 of an inch. 



Thus it cannot be said that there is any fixed average size to 

 this corpuscle, each investigator having an average size of his own. 



