224 



THE AMERICAN MONTHLY 



[December, 



adequately realize what is sufficient 

 caution in reaching a conclusion on 

 the subject. Nothing is more com- 

 mon than to see a determination ar- 

 rived at simply by measuring a series 

 of blood-discs of various kinds, and 

 comparing the results with what is ac- 

 cepted as a standard size of the blood- 

 corpuscles of various animals. Now, 

 while this may afford a correct deter- 

 mination, it is very far from certain to 

 do so. Dr. J. J. Woodward in M. M. 

 J. XIII, p. 65, pointed out many of the 

 discrepancies in the older measure- 

 ments of blood, and his own measure- 

 . ments, recorded in the same Journal, 

 where he describes his methods and 

 apparatus with a particularity com- 

 monly wanting in the earlier cases, 

 do not add any certainty to the mat- 

 ter. Dr. J. G. Richardson also, who, 

 so far as any recorded observations 

 show, has done more work on blood- 

 stains than all others together, in his 

 measurements of the blood of different 

 races at the Centennial, differs con- 

 siderably from the old measurements, 

 which are, however, still quoted as 

 standards. No longer ago than last 

 year measurements were published, 

 and by a good observer, in comparison 

 with the ^^Q-inch as the standard 

 size of human blood-corpuscles. Yet 

 I believe few microscopists, especially 

 if they have worked upon blood-meas- 

 urements, would now accept the 

 ^^Jo^'i^ch as very near a reliable stan- 

 dard of the size of human blood-cor- 

 puscles, notwithstanding the numerous 

 so-called " authorities " which still 

 flaunt the 52^0 standard. 



Let us consider for a moment how- 

 many real authorities we have, and 

 what constitutes an authority, on the 

 subject. Chief among those who early 

 made the measurement of blood-cells 

 a study are Leewenhoek, 1673-1720; 

 Hewson, 1773; Delia Torre, 1763; 

 Rudolphi, 182 1, and several others 

 might be named from the long list of ob- 

 servers up to about 1840. Then, in the 

 middle ages, so to speak, of this sub- 

 ject, Gulliver, from 1840 to 1846; 

 Robin, 1858 ; Schmidt, 1848 ; Virchou, 



1857 ; Kolliker, Harting and Valentine 

 before 1863 ; and Welcker, in 1863 ; 

 contributed further data ; and since the 

 period of about 1860-63, Richardson, 

 Mitchell, Woodward and Smith have 

 added something to the store of meas- 

 urements. Of all these and the nu- 

 merous other observers, scarcely any 

 two agree exactly in their measure- 

 ment of human blood, although the 

 variation between the most of them is 

 very slight. Now, as to the perfection 

 of the apparatus used, and the personal 

 skill and accuracy of the older obser- 

 vers, we know but little; but what we 

 do know is not calculated, in the light 

 of later work, to inspire confidence in 

 the reliability of their measurements 

 as compared with the later ones. Of 

 the grave defects in the methods of 

 Gulliver, Welcker and others, some 

 were pointed out by Dr. Woodward in 

 the paper cited ; and inhering in all 

 the measurements back of about 1850 

 is a considerable liability of error aris- 

 ing from too low powers and inferior 

 corrections of the objectives, and too 

 indefinite value of the micrometer 

 rulings used. This liability of error 

 has been reduced to almost nothing 

 by the perfection attained in objec- 

 tives and micrometers of late years. 



In most of the text books commonly 

 used as " authority " on the size of 

 blood-discs, we still find the older 

 measurements stated as the standard, 

 and almost without exception entirely 

 unverified by the author ! The " Mi- 

 crographic Dictionary," intended to be 

 an authority on matters purely micro- 

 scopical, gives (3d Ed.) Gulliver's 

 measurements; Carpenter and Hint, in 

 the language of Dr. Richardson, "fol- 

 low Gulliver," and so authors have 

 gone on following Gulliver until 

 the ^^'^^-inch has even acquired the 

 title of classic as the standard size 

 of human red blood-corpuscles. Ask 

 an expert for the authorities on the 

 size of blood-discs, and he will reel off 

 a string of names of authors " follow- 

 ing Gulliver " to the number of a 

 dozen or more, and will call them a 

 dozen "authorities," while in fact they 



