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Show 96 MR. GULLIVER ON THE BLOOD-CORPUSCLES. [Feb. 10, This is one of Professor Owen's views,-a "generalization" from a preposterous insufficiency of observations. After informing us that the rule is generally applicable to the placental and marsupial Mammalia, he adds that, " the blood-disks of the marsupial species which derives its nourishment from the greatest variety of organized substances, as the Perameles, which subsists on insects, worms, and the farinaceous and succulent vegetables, are larger than those of the (Spotted) carnivorous Dasyure, and those of the herbivorous Kangaroo, the blood-disks of the latter, like those of the placental Ruminant, being the smallest" (Lond. Med. Gazette, Dec. 20, 1839, p. 475). How completely this view is at variance with the facts may be seen in m y Tables of Measurements, of which he sometimes quotes the French translation by Prof. Milne-Edwards. The blood-disks are largest of all in the Elephant, a purely vegetable feeder, and in the Edentates, which do not subsist on the greatest variety of organized substances; while among Marsupials there are some species living on one kind of food, the Ursine Dasyure, e.g., that have larger blood-disks than those of the more omnivorous Perameles. They are larger in the piscivorous Seals and Otter than in the Pig, an animal well known to subsist on quite as great a variety of organized substances as the Perameles ; while the blood-disks of the Pig are not larger than those of the Tapir, Rhinoceros, and Ass, three other Pachyderms and well-known vegetable feeders. And similar examples are afforded by Birds and lower Vertebrates. No wonder, then, that a writer entertaining such opinions as to the food and blood-disks should embrace the additional error that their gradations of size are " insignificant " or " unimportant." But, notwithstanding his conclusions, the truth is that this question of size is both significant and important. In systematic zoology we have already seen that the size of the corpuscles frequently affords a good diagnostic, both of one order from another and between genera or species of a single order or family; as I have more fully shown in the Appendix to Gerber's 'Anatomy,' in the Notes to Hewson's Works, in various numbers of the * Philosophical Magazine' from 1839-42, in the second volume of the 'Journal of Anatomy,' and still further in the ' Proceedings' of the Zoological Society-with illustrative engravings in the volume for 1862 (p. 91), and in the 'Medical Times and Gazette' from August 1862 to December 1863. And in a physiological point of view the size of the blood-disks is still more important and significant in relation to respiration and animal heat, as described in Lecture IX., reported in the ' Medical Times and Gazette' for January 17, 1863, and in the abstract of another of my lectures in 'Scientific Opinion' for December 8, 1869. Indeed a field of experimental inquiry is thus opened which will surely yield a rich harvest when properly cultivated. What, for example, is the precise relation of animal heat to the proportion of the whole blood to the body ? What is the relation of that heat to the proportionate quantity or aggregate bulk of the blood-disks to the other parts of the blood ? How far is the animal heat affected, cceteris paribus, by the size of the blood-disks ? I know of no exact |
