1885.] 



MICROSCOPICAL JOURNAL. 



151 



An examination of the above 

 figures shows that the diflerence be- 

 tween the greatest and smallest aver- 

 ages of 25 corpuscles is .000028 or 

 1-35714 inch, a magnitude that may 

 be easily measured by any person 

 having the requisite skill and appa- 

 ratus. 



The diflerence between the highest 

 and lowest averages of 50 corpuscles 

 is .000015 or 1-66666 inch, which 

 approaches more nearly the limit of 

 micrometric measurement, though 

 probably not beyond it. 



The diflerence between the highest 

 and lowest averages of 75 corpuscles 

 is .000012 or 1-83333 i'^ch, which 

 approximates the limit of micrometric 

 measurement. 



The diflerence between the highest 

 and lowest averages of 100 corpuscles 

 is .00c XX) or i-iiiiii inch, which is 

 within the limits of personal and in- 

 strumental error, according to the 

 highest living authority upon this 

 subject, who writes, in substance, 

 that it is eas^^to measure 1-50000 inch, 

 but to be sure of i-iooooo inch is not 

 possible. 



The conclusion to be deduced from 

 the above figures is obviously that, 

 when a sufficient number of corpus- 

 cles are measured, there appears to 

 be an average size which varies within 

 ver)' narrow limits, which may possi- 

 bly be accounted for or at least is con- 

 sistent with personal and instrumen- 

 tal errors ; for though I have carried 

 out the figures to the sixth decimal 

 place, I have not the presimiption to 

 declare that the results can be relied 

 upon farther than the fifth place, and 

 have carried out the figures to the 

 sixth only to insure accuracy in the 

 fifth so far as possible. Another con- 

 clusion is, that granting for the mo- 

 ment that it is possible to identify 

 blood by measurements of the red 

 corpuscles, of which I am by no 

 means satisfied, it is reckless in the 

 last degree, if not criminal, to express 

 an opinion upon the measurement of 

 less than 100 corpuscles. To ex- 

 press an opinion upon the measure- 



ment of only 10 corpuscles, as I am 

 informed has been done in this sec- 

 tion within the last year or two, to 

 take the most charitable view of the 

 subject, betrays such culpable igno- 

 rance of a subject involving such mo- 

 mentous consequences as ought for- 

 ever to invalidate the testimony of 

 one who should swear so recklessly. 

 In a case involving the issue of life 

 and death it would be better to meas- 

 ure several hundred corpuscles. 



An examination of the unabridged 

 table of measurements, from which 

 the aljove summary is tabulated, dis- 

 closes the further fact, that by select- 

 ing the corpuscles it would be possi- 

 ble for a dishonest observer to make 

 the average much larger or smaller 

 than that above given, without the 

 possibility of detection ; a fact, the 

 bearing of which upon the value of 

 expert testimony upon this subject is 

 so obvious as to need no comment. 



It will be seen that I have not at- 

 tempted to draw any inference as to 

 the cause of the larger average size 

 of the corpuscles first measured. 

 Whether it was or not due to the 

 drugs exhibited din-ing the lieginning 

 of this work, is an interesting sul)ject 

 of inquiry, which must be reserved 

 for future examination. I expect to 

 continue these investigations, and at 

 some future day will publish the re- 

 sults, 



Marshall D. Ewell, M. D. 



Chicago, July 22, 1885. 

 o 



Conjugation of Bhabdoncma. 



In a late number of the yournal 

 of the Qiiekett Microscopical Club 

 Mr. T. H. Buftam has described some 

 newly-observed phenomena in the 

 conjugation of the diatom Rhabdo- 

 nenia arcuatum, that are of great 

 interest. It is not possible to do full 

 justice to the subject without. the plate, 

 but an account of the phenomena ob- 

 served may prove of interest to the 

 reader. 



The diatom grows in ribbon-like 

 filaments on marine algaj, the breadtli 

 varying from three to riine times the 



