CORRESPONDENCE. 
149 
microscope, and the corpuscles are then counted by means of a 
micrometer eye-piece. In counting the white corpuscles the blood is 
only diluted fifty times instead of a hundred, and a longer capillary 
tube is used than in the case of the red corpuscles. To count the 
latter it is not necessary to use a tube longer than twice the breadth 
of the field of the microscope, whereas for the former it is better to 
use one about ten times as long. The number of corpuscles thus 
counted gives what the author calls ' the actual richness of the blood,' 
i.e. the number of blood-cells in a unit of volume. To determine 
the * relative richness ' in the two kinds of corpuscles for any par- 
ticular blood, their number must be estimated separately, and then 
their relative percentage calculated. M. Malassez has already ob- 
tained the following results by his method. He finds that while the 
number of red blood-cells is uniform throughout the arterial system, 
in the venous it varies with the kind of organ from which the blood 
comes. Thus there is an increase in their number in the veins of the 
skin and muscles, especially during muscular action. There is also 
an increase in the blood from the secreting glands ; but, curiously 
enough, this is most pronounced, not during secretion, but when the 
organ is at rest. The red corpuscles in the splenic vein are most 
numerous when digestion is going on; whereas, in the intestinal 
veins, they are diminished at that time, and increased during fasting." 
COEEESPONDENCE. 
Yon Baer's and Mr. Badcook's B. polymorphus. 
To the Editor of the ''Monthly Microscopical Journal.'' 
3, Queen Steeet Place, Upper Thames Street, 
London, July 30, 1875. 
Sir, — In answer to Mr. Garner's letter of July 10, 1875, in 
your August number, I beg leave to say that, in the discussion to 
which he refers, the " doubt " was not as to the Bucephalus poly- 
morphus of Von Baer being " parasitical," because it was well known 
that the creature so named by him was found in that state only, and 
had been so found by other observers since. There had been a doubt 
previously expressed (see April number of Journal) as to whether the 
creature I had found, and which was the subject of discussion at the 
time alluded to by Mr. Garner, was really identical with Baer's 
Bucephalus, and this doubt begat another, viz. as to whether it was 
parasitical or not. I had not found it as a parasite, but always free ; 
and this perfectly free state, combined with certain structural and 
functional differences in comparison with Von Baer's Bucephalus poly- 
morphus, pointed to the bare possibility of its being another species 
or variety. In addition to other differences already pointed out by 
me to the Society, I may here mention that a few weeks since I found 
the creatures with two additional balls, in size and shape exactly like 
