ROBERTS, ON BLOOD-CORPUSCLES, 17% 
addition, a dark-red speck made its appearance on some 
portion of their periphery. The pale corpuscles took the 
colour much more strongly than the red; and their nuclei 
were displayed with great clearness, dyed of a magnificent 
earbuncle-red. Many of the nuclei were seen in the process 
of division, more or less advanced; and in some cells the 
partition had resulted in the production of two, three, or 
even four distinct secondary nuclei. 
These appearances were first observed in freshly drawn 
blood from the finger. Subsequently blood from the horse, 
pig, ox, sheep, deer, camel, cat, rabbit, and kangaroo, was 
examined in like manner. ‘The effect on the red ‘corpuscles 
(to which all the observations hereinafter recorded are ex- 
clusively confined) was, in each instance, the same as in 
human blood. 
The nucleated blood-dises of the oviparous classes, when 
treated similarly, yielded analogous results. The coloured 
contents were forthwith discharged ; the central nucleus 
came fully into view, and assumed a deep-red colour; the 
corpuscles expanded, they lost something of their oval form, 
and approached nearly, or sometimes quite, to a circular out- 
line. Lastly, there appeared on the periphery a dark-red 
macula, of a character and position resembling that seen on 
the mammalian blood-disc. Such a macula was detected in 
the fowl, in the frog, and in the dace and minnow, 
Owing, however, to the large quantity of molecular matter 
floating in the serum, and which was coloured by the magenta, 
difficulties were found in preparing specimens which carried 
conviction that the macula im question was not an adhering 
granule. It was also found that it required a nice adjust- 
ment of the relative quantities of the solution and of the 
blood to bring it out. It was only when the right proportions 
were hit, and especially when the discs were made to roll 
over in the field of the microscope, that the existence of a 
coloured particle organically connected with the cell-wall 
could be satisfactorily made out. The best specimens were 
prepared from human blood drawn in the fasting condition, 
and from the blood of a kitten two days old. 
From well-prepared specimens of human blood the follow- 
ing particulars were gathered (see fig. 1) :—Nearly every 
dise possessed the parietal macula ; it could be distinetly 
recognised in nine tenths of them, and in several of those 
in which it was not at first visible it came into view as the 
corpuscles revolved in the field. 
The macula was clearly situated in the cell-wall, and not 
in the interior of the corpuscle, Usually it appeared as if 
