368 
made out in freshly drawn corpuscles, that is to say, no out- 
line marking off the central portion of the corpuscle, fig. la ; 
but this appears to be a matter of degree. In perfectly fresh 
red corpuscles of the frog, and even in such corpuscles whilst 
still within the vessels of the mesentery, I have been able to 
distinguish the faint outline of the nucleus; and it seems to 
me that its greater or less distinctness depends on the condi- 
tion of the blood’ in the frog, that is to say, on the frog’s 
physiological condition. There is no doubt that, after the 
corpuscles are drawn and placed on a glass slide, the nucleus 
becomes more and more distinct in outline until it reaches a 
state of sharp definition. This delimitation of the nucleus 
must, however, be carefully distinguished from the granuia- 
tion of it caused by acids. Whilst both may, no doubt, be 
considered as depending on the coagulation of albuminoid 
substances, the first may be compared to that form of muscle- 
coagulation or rigidity which is resolvable, and does not indi- 
cate death ; whilst the granular condition is like the second 
or final form of cadaveric rigidity, and indicates an irreme- 
diable change. The mere delimitation, then, of the nucleus 
is not to be considered as always of post-mortem origin, but 
may occur more or less during life. 
Although, as remarked above, no trace of a wall to the 
blood-disc can be made out with the highest powers on 
normal specimens, yet the elasticity and preciseness with 
which they recover their form and their sharp outline deci- 
dedly suggest something like a limiting outer coat or 
pellicle. 
Amongst the normal blood-corpuscles in some perfectly 
fresh drawn, I observed the two copied in fig. 2a, a, in 
which the red-coloured portion of the cell or “ zooid,” as it is 
termed by Briicke, was shrunk and separated somewhat from 
the oval outline (cecoid) of the corpuscle, thus resembling, in 
some degree, corpuscles which have been acted on by certain 
reagents (boracic acid, Briicke; sugar, Hensen). I am not 
aware that such exceptional forms have previously been 
observed in normal unmanipulated blood. ‘They are of im- 
portance as tending to show that the separation into zooid 
and cecoid is not an entirely artificial phenomenon, since it is 
thus seen to occur in otherwise healthy corpuscles whilst 
circulating in the blood. The two corpuscles figured had in 
every other respect the usual form of the frog’s blood-disc. 
It is necessary to observe that they were obtained in the 
early spring from one of a number of “ winter frogs,” that is, 
frogs preserved in a cage through the winter. From another 
frog were obtained the remaining corpuscles figured in fig. 2, 
