IN RELATION TO ZOOLOGICAL DISTINCTION. 51 



the forms, in the number per cubic millimeter, and in the sizes of these 

 cells. In all warm-blooded animals, except birds, the erythrocytes are 

 non-nucleated, and they are circular, except in the Camelidoe, in which 

 they are oval. In birds, reptiles, amphibia, and fish they are nucleated, 

 and elliptical or oval, except in the Cyclostomata (lamprey) and Hippo- 

 campus (sea-horse) , in which they are circular. In the perch the extremi- 

 ties of the long diameters are somewhat elongated. 



The forms of the erythrocytes of different species have been studied 

 by a number of investigators, especially by Gulliver (Proc. Zoolog. Soc. 

 London, 1875, 474). (See p. 57.) Measurements of the ratios of thickness 

 to diameters do not show any important distinctions, but the ratios of the 

 long and short diameters of the elliptical and oval cells vary sufficiently 

 to be of zoological importance. Thus, the ratio of the diameters of the 

 humming-bird and the shrike are at a glance obviously different; the long 

 diameters of the corpuscles of the wild pigeon and of the august amazon 

 are practically the same, yet the difference in the short diameters is suffi- 

 cient to distinguish one from the other; the differences in the ratios of the 

 long and short diameters of the corpuscles of the rufous pigeon and the 

 wild pigeon, entirely apart from the difference in their long diameters, 

 positively differentiate one from the other, etc. 



THE NUMBER OF ERYTHROCYTES IN RELATION TO GENERA. 



In the bloods of all vertebrates the erythrocytes are in inconceivable 

 numbers. Franke estimates that the total number of cells in the human 

 body is 26,500,000,000,000 and that of this number 22,500,000,000,000 are 

 erythrocytes in other words, over four-fifths of the body-cells are red 

 corpuscles. Malassez estimated that there are in the human body about 

 341,000,000 to each gram of body-weight. The mere fact of the rela- 

 tively extraordinarily large number of these cells, entirely apart from the 

 extremely important hemoglobin content, is sufficient to prove their 

 great importance. In certain of the invertebrates the hemoglobin is in 

 solution in the blood plasma, but whether or not it functionates by virtue 

 of a combination with some protein or other substance which is an analogue 

 of the stromata of the erythrocytes has not, as far as we know, been shown. 



The number of erythrocytes per cubic millimeter of blood in any in- 

 dividual is so variable under both normal and abnormal conditions that the 

 figures recorded are to be regarded as being only approximate. But even 

 from such data it is manifest that there exist well-defined generic distinc- 

 tions. Malassez found variations in different species of mammals ranging 

 from 3,500,000 to 18,000,000 per cubic millimeter; in birds from 2,300,000 

 to 3,400,000; in osseous fish from 1,100,000 to 2,000,000; and in cartilagin- 

 ous fish from 140,000 to 230,000. Similar striking differences are shown by 

 the records of Welcker and others (Welcker, Zeit. f. rat. med., 1863, Ser. 

 3, xx, 257; Sherrington and Copeman, Journal of Physiology, 1893, xiv, 

 58; Vierordt, Archiv f. physiolog. Heilk., 1852, xi, 26, 327, 854, and 1854, 

 xni, 259; Malassez, Compt. rend. Acad. d. Sciences, 1872, LXXV, 1528; 

 Stolzing, Ueber Zahlung der Blutkorp., Inaug. Dissert., Marburg, 1856, 16; 



