VERTEBRATED ANIMALS. 269 



more evident when the concavity is increased by the partial shrinkage of 

 the corpuscles, which may be brought about by treating them with fluids 

 of greater density than their own substance. When floating in a suffi- 

 ciently thick stratum of blood drawn from the body, and placed under a 

 cover-glass, the red corpuscles show a marked tendency to approach one 

 another, adhering by their discoidal surfaces so as to present the aspect 

 of a pile of coins; or, if the stratum be too thin to admit of this, partially 

 overlapping, or simply adhering by their edges, which then become 

 polygonal instead of circular. The size of the red corpuscles is not alto- 

 gether uniform in the same blood; thus it varies in that of Man from 

 about the l-4000th to the l-2800th of an inch. But we generally find 

 that there is an average size, which is pretty constantly maintained 

 among the different individuals of the same species; that of Man may be 

 stated at about l-3200th of an inch. The following Table exhibits the 

 average dimensions of some of the most interesting examples of the red 

 corpuscles in the four classes of Vertebrated Animals, expressed in frac- 

 tions of an inch. Where two measurements are given, they are the long 

 and the short diameters of the same corpuscles. (See also Fig, 457). 



MAMMALS. 



Man 1-3200 



Dog 1-3542 



Whale 1-3099 



Elephant 1-2745 



Mouse 1-3814 



Camel 1-3254, 1-5921 



Llama 1-3361, 1-6294 



Java Musk-Deer 1-12325 



Caucasian Goat 1-7045 



Two-toed Sloth. . . 1-2865 



BIRDS. 



Golden Eagle 1-1812, 1-3832 



Owl 1-1830, 1-3400 



Crow 1-1961, 1 4000 



Blue-Tit 1-2313, 1-4128 



Parrot . 1-1898, 1-4000 



Ostrich -1649, 1-3000 



Cassowary -1455, 1-2800 



Heron -1913, 1-3491 



Fowl -2102, 1-3466 



Gull -2097, 1-4000 



REPTILES AND BATRACHIA. 



Turtle ..1-1231, 1-1882 



Crocodile 1-1231, 1-2286 



Green Lizard 1-1555, 1-2743 



Slow-worm 1-1 178, 1-2666 



Viper 1-1274, 1-1800 



Frog 1-1108, 1-1821 



Water-Newt 1-8014, 1-1246 



Siren 1-420, 1-760 



Proteus 1 400, 1-727 



Amphiuma 1-345, 1-561 



FISHES. 



Perch 1-2099, 1-2824 



Carp 1-2142, 1-3429 



Gold-Fish 1-1777, 1-2824 



Pike 1-2000, 1-3555 



Eel 1-1745, 1-2842 



Gymnotus 1-1745, 1-2599 



Thus it appears that the smallest red corpuscles known are those of the 

 Musk-deer; whilst the largest are those of that curious group of Ba- 

 trachia (Frog-tribe) which retain the gills through the whole of life; and 

 one of the oval blood-disks of the Proteus, being more than 30 times as 

 long and 17 times as broad as those of the Musk-deer, would cover no 

 fewer than 510 of them. Those of the Amphiuma are still larger. 2 Ac- 

 cording to the estimate of Vierordt, a cubic inch of Human blood con- 



1 These measurements are chiefly selected from those given by Mr. Gulliver, 

 in his edition of Hewson's Works, p. 236 et seq. 



8 A. very interesting account of the * Structure of the Red Corpuscles of the 

 Amphiuma tridactylum ' has been given by Dr. H. D. Schmidt, of New Orleans, 

 in the " Journ. of the Royal Microsc. Society," Vol. i. (1879*. pp. 57, 97. 



