and those of certain other Mammals. 67 
to the prejudice of innocent men, is more to be feared than the pos- 
sibiHty that an acquaintance with the true Hmits of our knowledge 
on this subject may sometimes be made use of in the unscrupulous 
defence of real criminals. I have, therefore, no hesitation whatever 
as to my duty in speaking of this subject at all, to speak the whole 
truth so far as it is known to me, and in so doing, I am happy to 
say I follow the practice of many of the best writers on medical 
jurisprudence. 
In the instance of the dog it might at first sight be supposed 
from the estimates of the average diameters of the red corpuscles in 
this animal and in man, as given by Gulliver and Welcker, the 
authorities most frequently cited in the modern text-books, that a 
certain small, but constant and measurable, difference existed, which 
might serve as the basis of a distinction in legal cases. This in- 
ference, however, is not only contrary to the facts of the case, but 
an examination of the original essays of the authors cited, shows 
that it is not borne out by their observations. 
The mean diameter of the red corpuscles of man, according to 
Gulliver,* is B-2V0 of an inch (= -00794 millimeter), while that of 
the red corpuscles of the dog is ^5*42^ of an inch (= •00716 mm.). 
With regard to his estimates for the human corpuscle, Mr. Gulliver 
says : f " We are only speaking now of the average size ; for they 
vary like other organisms ; so that in a single drop of the same 
blood you may find corpuscles either a third larger or a third smaller 
than the mean size, and even still greater extremes." According to 
this statement, the human red blood-corpuscles may vary in a single 
drop of blood from ^^Vtj- of an inch (= -00529 mm.) to ^Jwu 
( = • 01058 mm.). Mr. Gulliver tells us further, in the same para- 
graph, " My own estimate of the average size has been deduced from 
numberless measurements, frequently repeated during the course of 
several years, of corpuscles quite fresh and swimming in the blood, 
and in various artificial mixtures, as well as in the dry state." I 
have not, however, been able to find, in those of his papers which I 
has pithily said, that the testimony of the expert must be looked upon " as most 
dangerous clap-trap, and rather what we might expect to hear at some popular 
lecture, where the ' wonders of the microscope ' form the theme of declamation to 
a gaping audience, than the solemn asseveration on oath of a man of science in a 
court of justice." — 'Medical Times and Gazette,' April, 1857, p. 366. 
* George Gulliver, F.K.S., " Lectures on the Blood of Vertebrata," ' Medical 
Times and Gazette,' vol. ii., of 1862, p. 101, et seq. ; " On the Eed Corpuscles of the 
Blood of Vertebrata," &c., ' Proceedings of the Zoological Society of London,' 1862, 
p. 91 ; the Sydenham Society's edition of ' The "Works of William Hewson,' 
London, 1846, p. 216, et seq. ; Appendix to ' Gerber's Elements of the General and 
Minute Anatomy of Man and the Mammalia,' London, 1842, p. 31, et seq. ; "Ob- 
servations on the Blood-corpuscles or Eed Disks of the Mammiferous Animals," 
'London and Edinburgh Philosophical Magazine,' vol. xvi. (1840), pp. 23, 105, 
and 195; also vol. xvii., pp. 139 and 325; also vol. xxi. (1842), p. 107. For a 
list of other papers referring to the blood-corpuscles of various animals, see ' The 
Works of William Hewson,' above cited, note to p. 236. 
t 'Medical Times and Gazette,' vol. ii., of 1862, p. 157. 
