Photography to Micrometry. By Dr. Woodward. 151 
individuals, but also between different parts of the very same drop 
of blood. 
Now it is true, as was shown by the measurements of human and 
dog's blood, published in my former paper, that the mean diameter 
of the corpuscles in a given sample of human blood is often rather 
larger than the mean of a sample of dog's blood selected for com- 
parison. I may even go further, and say that the average of all 
the measurements of human blood I have made is rather larger 
than the average of all the 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 their average size is 
larger than that of many samples of human blood. This was clearly 
shown by the measurements published in my former paper, as it is 
by those which are appended to the present paper, and will be by 
any fair series of comparative measarements. 
Thus I note here with pleasure that, since the publication of 
my former paper, Professor Gulliver, whose measurements of blood- 
corpuscles are those most frequently cited in English works, has 
published an extended and revised table of measurements of the 
blood- corpuscles of vertebrates, prefaced by some remarks, in the 
course of which he expressly affirms the futility of attempting to 
distinguish human blood in criminal cases.* 
I conclude this paper with a table of measurements of the red 
corpuscles of man, the dog, and the guinea-pig, as dried in thin 
films on the glass micrometer, and measured by the photographic 
method, above described. A print of each negative accompanies 
this pa^.-er, t and copies of a selection of them will shortly be sent 
to convenient places in the larger cities, with the view of making 
them accessible to those who may be interested in this question. 
The table gives the number of corpuscles measured on each 
negative, the diameter of the maximum and minimum, and the 
mean. The maxima and minima are given, like the mean, in 
millionths of an inch, because, although the measurements w^ere 
* George Gulliver, " Observations on the Sizes and Shapes of the Eed Cor- 
puscles of the Blood of Vertebrates," &c., ' Proc. of the Zoological Society of 
London,' June 15, 1875, p. 474. The passage referred to in the text is on page 
484 : " before noticed, the magnitude of the corpuscles in a single species, not 
excepting the human, is liable to variations within certain limits ; and there com- 
monly appear in one field of vision of the same corpuscles ditiereuces amounting 
to at least one-third larger and smaller than the average. Hence, as regards the 
medico-legal question, however truly a careful observer (Dr. Joseph G. Eichardson, 
' Monthly Micros. Journ.' Sept. 1874) may have distinguit-hed, by comparative 
measurements of the corpuscles, stains of human blood from those of the sheep or 
ox, this kind of diagnosis, as Dr. J. J. Woodward observes ('Monthly Micros. 
Journ.' Feb. 1875), would be inetfectual in some probable and more possible 
cases. It should be borne in mind, too, that in the apyrensemata " (i. e. tlie mam- 
malia) "the membranous bases of the blood-disks, when deprived of their colour 
by maceration in water, are about a third smaller than the unaltered corpuscles." 
t A series of admirable photographs were sent with the paper, and can be 
seen by anyone who is interested in the matter. — Ed. ' M. M. J.' 
VOL. XVI. M 
