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Show 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 Tragulus, 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 approximation 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 Ferce. 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 Paradoxures aud Viverras the blood-disks are not larger than in the Wapiti, Elk, and Sambur Deer, and in the Aurochs 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, cceteris 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, notwithstanding the 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 pyrensematous 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, cceteris paribus, is likely to be an aberrant one in its general organization. All m y observations support this view, as is exemplified 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 instance. Again, m y discovery of the singular minuteness of the blood-disks of Tragulidae 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. |