Diagnosis of Blood Stains. By J. G. Richardson. 213 
1 3. On some Undescribed Testaceous Khizopods from the North 
Atlantic Deposits, (pp.7.) ' Monthly Micros. Journ.,' Feb. 1869. 
14. On the Khizipods as embodying the Primordial Type of 
Animal Life. (pp. 7.) ' Monthly Micros. Journ./ April, 1869. 
Y. — Note on the Diagnosis of Blood Stains. 
By Jos. Gr. EiCHARDSON, M.D., Microscopist to the Pennsylvania 
Hospital, Philadelphia, U.S.A. 
One or two points in my paper " On the Yalue of High Powers in 
the Diagnosis of Blood Stams' * having been somewhat sharply, 
although courteously criticized in these pages by my friend Dr. 
J. J. Woodward, U. S. Army of Washington, D.C., I wish to add 
a few words in explanation. 
Dr. Woodward states that he writes to point out that it is 
" never in the power of the microscopist to affirm truthfully on 
the strength of microscopical investigation, that a given stain is 
positively composed of human blood, and could not have beeu 
derived from any animal but man." With this proposition I fully 
agree, contending, however, that whilst it is literally true, it is not 
the whole truth, because, as may often happen in medico -legal 
practice, when evidence other than microscopical narrows down the 
conditions of the case to the question. Is this stain human blood or 
that of an ox, pig, or sheep? the microscopist can from fair 
specimens of blood spots as ordinarily produced, affirm truthfully 
that the "given stain is positively composed of human blood," 
should it really be so. This second statement I believe Dr. W. 
will admit, as an additional part of the truth, and if not I under- 
take to convince him (as I have some other candid doubters among 
my friends), by incontestable evidence. 
Our real difference then is not mainly upon matters of fact, but 
on a matter of opinion, respecting the just prominence which 
should be given to the circumstance that " the blood-corpuscles of 
a few mammals approach so nearly in size to those of man as to 
render their distinction doubtful," a fact, be it observed, which I 
thus in these words explicitly mention, on p. 153 of my essay in 
this Journal for September, 1869,t of which my paper above 
referred to is avowedly a continuation. 
Now, whilst I honour Dr. Woodward for the discharge of what 
* See the 'American Journal of the Medical Sciersces,' July, 1874, and this 
Journal for September of the same year. 
t And also 'Handbook of Medical Microscopy,' p. 288. Philadelphia. 1871. 
