1884.] 



MICEOSCOPICAL JOURNAL. 



27 



C. M. Vorce, F. R. M. S., upon 

 The Microscopical Discrimination of 

 Blood. The statement was there 

 made — in which I fully concur — that 

 the hitherto accepted standard of the 

 size of the human red blood-corpuscle 

 was erroneous, and that, if measure- 

 ments were carefully made vs^ith the 

 best modern appliances, Gulliver's 

 standard of Wtwt of an inch " will be 



3200 



found to be nearer 



inch than 



is generally supposed." 



I have hitherto pointed out the un- 

 reliability of the so-called ' ' standard 

 measurements" of blood-corpuscles, 

 and have cautioned observers against 

 accepting them as a means of differ- 

 entiating human and animal red blood- 

 corpuscles. The size of any minute 

 object must be determined by the ob- 

 server himself, without regard to the 

 published opinion of another. Let 

 him determine the size of the object 

 viewed by his own standard, which is 

 sufficiently reliable for his own pur- 

 pose in making comparative measure- 

 ments. How many of the ruled spaces 

 of his micrometer does the object oc- 



cupy 



? That is all he desires to know. 



It matters not whether he calls it the 



TToTT *^f ^^^ inch or the -^-gVif ^^ ''■ ^^^' 

 long. What is the measurement on 

 his mici-ometer ? That will not vary — 

 it will always represent precisely 

 the same member of lines to him, 

 which, for purposes of comparison, 

 are perfectly trustworthy. To the 

 practical worker in micrometry, it is 

 apparentthat this plan must be adopt- 

 ed until, as Mr. Vorce suggests, an 

 identical standard of measurement is 

 adopted, with which all our micro- 

 meters are compared and rated. Un- 

 til then, every observer must maintain 

 his own standard. 



The editor of the Am. Monthly 

 MiCR. Journal, in commenting upon 

 Mr. Vorce's paper, makes the follow- 

 ing statement : "If, as the author 

 states, it be found that the average size 

 of human blood-corpuscles is ^^[Vo ^^^" 

 stead of -gYTo ^^ ^" inch, it needs no 

 words to point out how uncertain are 

 the assumptions upon which expert 



testimony has been founded." And 

 again, " It is well, therefore, that the 

 sources of error should be set forth ; 

 and we trust the article w^ill prove a 

 serious obstacle to those who, with un- 

 due assurance, venture to recognize 

 human blood." 



It would seem that the Editor does 

 not .take into consideration the fact 

 that, if, according to Mr. Vorce's 

 measurements of the human blood-cor- 

 puscle, it is found to be nearer ^iW' 

 according to his micrometer, that the 

 corpuscle of animals must vary in like 

 ratio. If Gulliver concluded the hu- 

 man corpuscle to average -jgVo ^^ ^" 

 inch, and the pig corpuscle j^VtT' then, 

 would not Mr. Vorce, in applying his 

 micrometer to the human corpuscles 

 and finding them to measure -gxoir ^^ 

 an inch, find also, by the same rule, 

 the pig's to measure -^-^-qq of an inch 

 or smaller.? Would not the prevail- 

 ing difTerence in size still exist — as 

 shown by Gulliver — when measured 

 by Mr. Vorce.'' If not, why not.'' 

 Thad. S. Up de Graff. 

 Elmira, N. Y. 



[To the question just stated we re- 

 ply, certainly the relative sizes would 

 be the same. The important question 

 still remaining unsettled is, whether 

 the difference in the size of human 

 blood-corpuscles and those of certain 

 domestic animals is sufficient to enable 

 them to be distinguished with cer- 

 tainty. — Ed.] 



o 



Microscopical Technic. 



I. APPARATUS AND MATERIAL. 



The present article upon this sub- 

 ject is intended as an introduction to 

 a series which has been more fully an- 

 nounced in another column. It em- 

 braces a brief description of the ap- 

 paratus and material required for 

 mounting. At the end of the article 

 will be found a list of the essentials, 

 which the beginner would do well to 

 obtain. It is recommended that all 

 the apparatus should be prepared or 

 purchased at the beginning, as noth- 



