*Jo" ni sJptTiS?'] Corpuscles in Blood-stains. 1 53 
to make the following calculation, which tends to show that the 
outer portion of the corpuscles (whether it be merely condensed 
viscid material, or a true cell-wall composed of membrane distinct 
in composition from hsemato-crystallin) is of an inelastic character. 
Ten red globules of freshly-drawn human blood magnified almost 
1800 times were measured with the micrometer while standing on 
their edges, both in length (as so placed) and in thickness, their 
mean diameter being found equal to s^^g and their mean of greatest 
thickness y^^s 5 of an inch. From these data, estimating the total 
surface of the globule as approximatively equivalent to ninety-six 
one hundred and sixty-firsts of a ring '00029886 in outside 
diameter, and * 00007478 of an inch thick, plus double the super- 
ficies of a segment with a versed sine of •00003739 cut from 
a sphere having •00017718 radius, I calculated the area of the 
hypothetical cell- wall to be "00000017932 of a square inch ; by 
further computation, it was found that this amount of membrane 
would cover a globe "00023891 of an inch in diameter, which 
number so nearly coincides with that expressing the diameter of 
the red disk, when rendered spherical by the action of pure water, 
viz. ' 00023332 (4^6^) of an inch, that I think we may fairly con- 
clude that, although the shape of the corpuscle is thus altered, its 
parietes undergo no real dilatation in the process ; further, the cor- 
rugated appearance assumed by the corpuscle when any portion of 
its internal constituent is removed by exosmosis afibrds some 
evidence that, however much the cavity is decreased, its limiting 
membrane suffers no actual diminution in superficial area. 
Although it must be admitted that the blood corpuscles of a few 
mammals approach so nearly in size to those of man as to render 
their distinction doubtful, yet for the practical testing of blood- 
stains in criminal trials we will rarely find that such a decision 
is necessary, since, as a rule, justice only requires that a positive 
diagnosis shall be made between human blood and that of animals 
which are commonly slaughtered for food, such as the ox, the sheep, 
the pig, or of birds, as for example, chickens, ducks, &c., in regard 
to all of which I believe when the disks have not undergone dis- 
integration, a first-rate 2V inch objective will enable us to determine 
easily and beyond all question. 
I would suggest to any one about undertaking such an in- 
vestigation, that he first accustom himself to the appearance of 
decolourized blood corpuscles, and at the same time test the power 
of his instrument by repeating Experiment 3rd, as detailed above, 
on a fragment of blood clot recently desiccated upon paper or glass. 
Experience has shown that dried stains upon hard, smooth surfaces, 
such as buttons, studs, &c., most readily exhibit the corpuscles ; 
next to these in case of detection, are stains upon paper collars or 
cuff-^, and upon highly glazed linen ; then those upon unstarched 
VOL. II. M 
