l88 Cleland and Johnston, Red Blood Cells. [isf'jan 



Relative Dimensions of the Red Blood Cells of 

 Vertebrates, especially of Birds. 



By J. Burton Cleland, M.D., Ch.M., and T. Harvey Johnston, 

 M.A., D.Sc. 



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 ex- 

 amining. 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 water- 

 birds, 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, how- 

 ever, must not be accepted as fully accurate until confirmed by 

 many more observations. 



♦Bruce, Hammerton, and Mackie, "Proceedings Roy. Soc," 1910, B. 558, 

 pp. 490, 497. 



