THE MICROSCOPE. 215 



revealed by. your own micrometer and your personal skill. A cor- 

 puscle measured by two different individuals, by different micro- 

 meters, will not likely report the same named portions of an inch, or 

 millimeter. But, each observer will agree with his own measure- 

 ments and will recognize them when applied to yarious specimens. 

 Each will be able to declare for himself whether the blood sub- 

 mitted be that of man or dog, and they will agree perfectly, accord- 

 ing to the tests here set forth, although they may record a different 

 named size to the corpuscle. 



To the quotation from Dr. J. J. Woodward, to wit: "The 

 average of all measurements of human blood I have made is rather 

 larger than the a\erage of all measurements of dog's blood. But it 

 is also true that it is not rare to find specimens of dog's blood in 

 which the corpuscles range so large that the average size is larger 

 than that of many samples of human blood:" I can only say that in 

 a very extensive examination of the blood of the setter, pointer, 

 spaniel, grayhound, rat-terrier, newfoundland, spitz, poodle, and the 

 common cur — all treated in precisely the same manner and under 

 the same conditions — I have never found a solitary instance where 

 the red corpuscles averaged as large as those of man. Yet, I would 

 not rely solely upon the size of the corpuscle, in determining 

 whether it was from human blood or not, but accept it as one of the 

 factors in such determination. In addition to the conditions that 

 enter into the differentiation, and already foreshadowed, are. the ad- 

 ditional ones of the density of color, and the form of the crystals of 

 haematin. 



I will not weary you with the detail of experiments under this 

 latter head and extend this, my preliminary article, that has already 

 become too prolix. I did not intend to have written anything upon 

 this subject until my investigations were completed, that I might 

 support my statements with facts and figures gleaned from my 

 laboratory note book, and should have adhered to that resolution 

 but for the ridiculous position in which Prof. Stowell's article left 

 me. By the time the winter is ended, I hope to be able to complete 

 the work but now fairly begun; and, whether I succeed or not in 

 making it possible — in every instance — and by every microscopist, 

 to distinguish between the blood corpuscles of man and dog, I shall 

 at least acquaint you with the facts gleaned from my honest en- 

 deavor. 



