30 



SPECIFICITY OF THE BLOOD OF VERTEBRATES 



TABLE 6. Proportion of blood to body-weight in different animals, according 



to figures of Welcker. 



While it will be seen (tables 6, 7, and 8) that the proportions recorded 

 by different observers in studies of a given species differ (differences insepa- 

 rable from the methods of determination and the variations that occur in 

 the quantity of blood in any given individual even under perfectly normal 

 conditions), the mean figures may be regarded as being sufficiently approx- 

 imate for purposes of comparison. The range of mean values for the differ- 

 ent classes is between one-forty-ninth (2 per cent) for fish and one-twelfth 

 (8.3 per cent) for birds ; in other words, in proportion to body-weight fish 

 have less than one-fourth the quantity of blood found in birds. Comparing 

 monkey and man, the proportion in the monkey is distinctly lower. Only 

 two monkeys were studied, one young and the other veiy young, the values 

 being 1 : 11.1 (9.02 per cent) and 1 : 13.6 (7.35 per cent), respectively. 

 Among the members of the different orders, it will be found that the figures 

 are higher in birds than in carnivora, herbivora, and rodents ; higher in her- 

 bivora, especially in the horse, than in carnivora and rodents ; and higher in 

 carnivora than in rodents. While Welcker's table, showing a comparison of 

 different classes, leads to the assumption that, with the exception of birds, 

 the proportion of blood is higher as the animal is higher in the scale of 

 life, it will be seen by comparing the values in tables 7 and 8 that such 

 relationship is open to so many exceptions as to be untenable. When, 

 however, comparisons are restricted to an order or class, without reference 

 to the scale of life, the values give the impression of zoological distinctions. 



