Relative Dimensions of the Red Blood Cells of Vertebrates, especially of Birds
J. B. Cleland, T. H. Johnston · Emu - Austral Ornithology · 1912
During the course of an examination of smears of blood from Australian birds for parasites, we noticed with much interest that the red cells of one of the Ardeiformes, Notophoyx novce-hollandia, were distinctly larger than those of other birds we had hitherto examined belonging to the Passer if ormes.As the first-named is a presumably older group phylogenetically, it occurred to us that it might be of value to systematically measure the red cells of the various vertebrates that we had an opportunity of examining.This work was already in progress when we noticed a statement in The Sleeping Sickness Bulletin (vol.ii., No. 19, 1910, p. 245) * as to the sizes of the red cells in blood ingested by tse-tse flies {Glossina palpalis), and the inference therefrom as to the source of the blood.The following standards were taken : -" Standard amphibian (crocodile) [sic], 15.4 microns.Standard avian (Hornbill), 13. i microns."The average measurements of the red cells in 20 flies are given' Of these 2 were over 15, 11 between 14 and 15, 6 between 13 and 14, and I was 10.6 mic.Those under 14 were attributed to birds.This agrees perfectly with our findings, as it is only occasionally in odd cells that we have found a reading under 14 mic. in the blood cells of reptiles.We have, however, especially in waterbirds, such as Grebes, Herons, and Charadriiformes, found red cells reaching to 15 mic, and as these birds would, we presume, frequent the lake-shore, where the flies were caught, it is possible that the number of cases in which birds' blood was present was under-estimated -in fact, it is not beyond the bounds of possibility that they all owned this origin.This is perhaps accentuated by the fact that the average reptilian corpuscle, in our hands, is usually well above 15 mic.It must be clearly understood that our measurements were taken from dried blood-films stained by Giemsa's solution, and not from films treated by the better-fixed wet methods.Several cells were measured in each case, but time would not permit of a long series of measurements, with more accurate average results.In the case of well-prepared slides of mammals and birds this is of little consequence, as all the cells are practically of an identical size.In the cases of reptiles and batrachians considerable variations, however, occur.The object of this paper is to indicate what we believe are useful additional means for showing the relationships of groups of vertebrates to each other.Our actual figures, however, must not be accepted as fully accurate until confirmed by many more observations.