58 SPECIFICITY OF THE BLOOD OF VERTEBRATES 



from the others by the mean sizes of the corpuscles, but even individuals 

 belonging to each class. (Plate A.) 



The nearness of the diameters of the erythrocytes of certain of the 

 domesticated animals to those of man is a matter of considerable impor- 

 tance, chiefly because of its medico-legal bearing, and it is yet an open 

 question if the corpuscles of the dog, and especially of the guinea-pig, 

 can with positiveness be distinguished from those of man. The mean 

 measurements found by White (expressed in (i) are: man 8.01, guinea-pig 

 7.47, dog 6.87, pig 6.07, ox 5.44, sheep 4.75, and goat 3.69. Not only 

 are these measurements sufficiently different to be significant, but the 

 variations in the ranges in the sizes in the different species are peculiar. 

 Particularly striking is the wide range in the pig and the narrow range in 

 the goat, the limits of the former being 3.75 to 8.50 and of the latter only 

 3 to 4.5. 80.5 per cent of the corpuscles of man ranged between 7.5 and 

 8.5, 90 per cent of the dog between 5 and 7.5, 80 per cent of the pig between 

 5 and 7.25, 95 per cent of the ox between 4.75 and 6.25, 89 per cent of the 

 sheep between 4 and 5.25, and 96 per cent of the goat between 3.45 and 4.25. 



There are also certain relationships between the mean size of the cor- 

 puscles and the size of the species. Gulliver states that, if "we confine 

 the observations to small natural groups of the class, such a relation will 

 plainly appear in a rule that the largest corpuscles occur in the largest 

 species and the smallest corpuscles in the small species of a single order or 

 family. This relation is well shown in ruminants, rodents, and edentates, 

 and even in fera3, which offer some exceptions; the largest corpuscles are 

 found in the big seals and the smallest in the little viverras and paradox- 

 ures. In fine, though this rule is applicable only to single orders or lower 

 sections of apyrensemata, it extends to the whole class of birds, but neither 

 to the reptiles, batrachians, nor fishes, except in partial instances, which 

 seem to be rather indeterminate or accidental than regular." Attempts 

 to trace a relationship between the number and size of the corpuscles and 

 the speed of the animal's movements have proven negative. The very 

 small and numerous corpuscles of the chevrotain have been associated with 

 the fleetness of the animal ; while, on the other hand, the enormously large 

 and comparatively few corpuscles in the amphiuma have been associated 

 with sluggishness. Such assumptions have been founded upon insufficient 

 or erroneous data. There is, as a rule, an inverse relationship between the 

 number of corpuscles per cubic millimeter and the mean diameter, but 

 even in closely related genera this relationship may not exist. 



CERTAIN PROPERTIES OF THE ERYTHROCYTE IN RELATION TO GENERA. 



There are certain peculiarities shown by the erythrocytes of different 

 species which are of zoological significance. The well-known property of 

 the erythrocytes of mammalian bloods to form rouleaux after the blood is 

 shed has not been observed in the case of bloods having nucleated cells, 

 except in the lamprey. This difference may be purely mechanical, and due 

 to the nuclei preventing the approximation of the sides of the erythrocytes. 



There are certainly differences in the specific gravities and coloration of 

 the erythrocytes of different species. 



