1870.] MR. GULLIVER ON THE BLOOD-CORPUSCLES, 95 
Capybara, and the smallest in the tiny Harvest-mouse ; while in the 
whole class of Birds the rule in this respect, in conformity with the 
comparative uniformity of their general organization, proved to be 
like that rule for a single order of Mammalia. .On the contrary, 
with such greater divergences of general organization as occur in 
Reptiles and Fishes there are corresponding diversities in the blood- 
disks. 
And the present observations conform to this view as to the size of 
the red blood-corpuscles in a mammalian order. Among Ruminants 
the woodcut shows these corpuscles smallest in the diminutive Tra- 
gulus, larger but still small in the bigger Moschus, with much 
increase of size in the great Moose-deer. And they are largest of 
all in the biggest Edentata, so that this order is now proved to be 
characterized by larger blood-disks than have yet been found in as 
many different genera of any other order of Mammalia. 
In many species of different orders there may be such a near ap- 
proximation in the size of the corpuscles as to make them worthless 
as diagnostics between one order and another. For example, some 
of the larger Ruminants could not be distinguished by this character 
from several Fere. In the Seal, indeed, these corpuscles are about 
the same size as in Man, and only slightly smaller in the Otter and 
Dogs; but in the Paradorures and Viverras the blood-disks are not 
larger than in the Wapiti, Elk, and Sambur Deer, and in the Au- 
rochs and other Oxen. 
But in closely allied and true members of a single natural family 
the characters of the blood-disks, as already shown, may afford an 
excellent diagnostic between that and another family. In such a 
family the blood-disks are so much alike that their size, ceteris 
paribus, is only largest among the big species and smallest among 
the little species. Shortly after the discovery by M. Mandl of the 
oval shape of the red blood-corpuscles of the Dromedary and Paco, 
I confirmed it, and discovered that these corpuscles have the same 
shape in all the other members of this family—also that, notwith- 
standing tne oval figure of these blood-disks, they resemble those of 
other Ruminants in structure and size, and by no means approach 
in either of these respects to the oval corpuscles of pyrenzematous 
vertebrates (Med. Chir. Trans. Nov. 26, 1839, vol. xxiii.). 
But when the blood-disks of one species differ remarkably in size 
from those of several other species of a single natural family, that 
species, ceteris paribus, is likely to be an aberrant one in its general 
organization. All my observations support this view, as is exempli- 
fied by Hyrax capensis, Bassaris astuta, Cercoleptes caudivolvulus, 
and other Mammalia. And we have already seen that Moschus, if 
still included with Tragulus, would be an equally remarkable in- 
stance. Again, my discovery of the singular minuteness of the 
blood-disks of Tragulidze would indicate that this is really a distinct 
natural family, though I know not that we have any other group of 
equally small Ruminants for comparison. 
The opinion that the size of the blood-disks is connected with the 
kind of food on which the animal lives has never been confirmed. 
