569 
the blood being perfectly fresh, and placed directly from the 
animal’s finger on to the microscope-slide. It seems highly 
probable that the red blood-corpuscles of the frog present, at 
different seasons of the year, somewhat different properties, 
as I shall have again to remark in speaking of the action of 
ammonia upon them; and it is hkely that these curious 
forms are extreme examples of this variability. The corpus- 
cles drawn in fig. 2 are remarkable for their irregular shapes ; 
they were quite exceptional in the blood from which they 
came, by far the majority being of the usual oval contour; 
but in this same blood nearly all the corpuscles presented 
that curious frilled appearance of the margin which can be 
brought about by the action of many reagents in ordinary 
corpuscles. That this appearance was not due to any change 
after separation from the body I am tolerably certain, and I 
have observed such a condition of the corpuscles in quite 
fresh blood from other frogs. It is comparable to the so- 
called “ thorn-apple form” of the human blood-corpuscle (fig. 
_ 18 e). The frilled appearance seen in these corpuscles is due 
to the commencing radial cleavage of its substance, succes- 
sive stages of which phenomenon are seen in fig. 7 a, 5, c. 
4. The normal appearance of the human red blood-cor- 
puscle.—The human red blood-corpuscle is a circular bicon- 
cave plate. It is, however, erroneous to regard this as the 
only normal form. In the blood of perfectly healthy persons I 
have frequently noticed the ‘‘ thorn-apple form ” (fig. 18 e), so 
immediately after the shedding of the blood, that I do not 
doubt that these forms existed in the circulating fluid. My 
own blood almost invariably presents these thorn-apple forms 
in large number, and I have not yet been able to connect 
their presence, or greater or less quantity, with any particular 
condition of health or nutrition. In addition to the thorn- 
apple form, my own blood frequently presents what I will 
term the “single” and ‘‘double watch-glass forms.” In 
these corpuscles, in place of a concavity on each face of the 
dise, we have a very large convexity, of delicate appear- 
ance, and paler than the rim or margin of the corpuscle. 
Sometimes only on one face of the corpuscle is there this 
swelling out, and then the appearance is that of an old- 
fashioned watch seen from its side, the darker coloured rim 
of the corpuscle representing the metal watch, and the swell- 
ing representing the convex glass. Often these convexities 
appear on both sides of the corpuscle (fig. 18¢). I do not see 
any reason for attributing these forms to changes occurring 
in the corpuscle after it has been shed. I have observed 
them (with Hartnack’s No. 10 4 immersion), with the greatest 
