BLOOD OF MAMMALS. 515 



by the size of the blood-discs. 1 In every individual a certain range 

 of size was presented, and the two extremes and the average were 

 recorded : thus, in the Indian Elephant, the largest blood-discs 

 were twice the size of the human, and the smallest was not less 

 than -j-Vo th, the average being ^Vo * n f an inch. 2 In the Che- 

 vrotain ( Tragulus Kanchil) the average diameter of the blood-disc 

 was -j-g-^o-o th inch. In the Giraffe the average size of the blood- 

 discs was -jyVo th inch, or nearly one-third smaller than those of 

 Man ; the two extremes were 4 oVo ^ n (f ew ^ n number), i^th of 

 an inch (more in number). ( The result of the examination of 

 the blood of the largest of the ruminatino; tribe indicates that the 



< j ^ - 



size of the blood-discs relates to the condition of the whole organi- 



o 



sation rather than to the bulk of the species. It would appear from 

 the examination of the blood-discs in the goat, sheep, and ox, that 

 an unusually small size of the blood-discs was associated with the 

 peculiarities of the ruminant structure.' 3 This generalisation has 

 not been affected by later observations. MAXDL 4 had discovered 

 in the Dromedary that the blood-discs were elliptic. I confirmed 

 the fact, giving the long diameter of the average- sized discs as 

 TsVo tn inch? the short diameter -ggVoth inch; but I remarked 

 that among the elliptical discs were a few of a circular form. 

 Extending the observation to the smaller South American species 

 of the aberrant ruminant family, I found the elliptical form to pre- 

 vail in the blood-discs of both Llama and Vicugna. 5 In the latter 

 the average dimensions were, in long diameter -jj-^-^, short diameter 

 g-^-j-g. Mr. AVhartou Jones subsequently observed blood-discs 

 of a circular form with the more numerous elliptic ones in the 

 Llama. 6 These exceptional instances to the Mammalian form of 

 blood-disc are not associated with any other approximation to the 

 oviparous type : the oval kind are equally non-nucleate with the 

 ordinary circular blood-discs, and adhere to the ruminant charac- 

 teristic of minuteness of size. Within the limits of that natural 

 group, it will be observed that there is a ratio between the size of 

 the blood-disc and that of the animal. But such ratio is quite 

 inapplicable to the Mammalian class generally. If the Camelidce 

 repeat a reptilian shape of blood-disc, the Sloths have the largest 

 blood-discs in proportion to the body : but neither one nor the 

 other character occurs in the Monotr ernes and Marsupials which 

 combine the greatest proportion of oviparous characteristics in 

 their Mammalian organisation. In the Echidna and Ornithorhyn- 



1 CLXXIX". 2 Ib. p. 284. 3 Ib. p. 284. 



4 CLXXXII", p. 1060. 5 Ib. p. 475. 6 CLXXXI". p. 73. 



1,1,2 



