216 FUNCTIONS OF NUTRITION, 



minous matter, which forms a substratum for its other ingredients. 

 This substance is less soluble in water than hemoglobine, and remains 

 behind when the latter has been dissolved out, leaving the globules de- 

 colorized and reduced in volume. The exact condition of hemoglobine 

 in the blood-globule, and its mode of union with the colorless sub- 

 stratum, are not positively known. Preyer calculates that the water 

 of the globule is insufficient to hold in solution the quantity of hemoglo- 

 bine present ; and on the other hand, as the crystals of hemoglobine are 

 doubly refracting, while the fresh globules are not so, the hemoglobine 

 cannot exist in the globules in a solid form. So far as we can judge, the 

 two substances are uniformly united in a condition of semi-fluidity ; 

 but the hemoglobine, being more easily affected by various dissolving 

 agents, may be extracted by this means from the mass of the globule. 



The avidity of hemoglobine for free oxygen, and its readiness to part 

 with this substance under favorable conditions, cause it to assume alter- 

 nately the two different forms of " oxyhemoglobine " and "reduced 

 hemoglobine " (page 94). The former gives its bright scarlet hue to arte- 

 rial blood, the latter is the dark purple coloring matter of venous blood. 



Red Globules of the Blood in Different Classes of Animals. In all 

 vertebrate animals the red globules contain a coloring matter identical, 

 in its optical and physiological properties, witty that of human blood ; 

 but they present varieties of form, size, and structure more or less char- 

 acteristic of different classes, families, and species. 



In the mammalians, or warm-blooded quadrupeds, the red globules 

 have without exception the same homogeneous structure as in man. 

 They have also the same circular disk-like figure, except in the family 

 of camelida? (camel, dromedary, lama), where the disks are oval. Their 

 size varies much in extreme cases, the smallest known being those of 

 the Java musk-deer, an animal not larger than a rabbit, which have a 

 diameter of 2.50 mmm., while the largest are those of the elephant, 

 which measure 9.20 mmm. Their size, however, does not always cor- 

 respond with that of the animal, since those of the cat are larger than 

 those of the sheep, and those of the rabbit larger than either. The fol- 

 lowing list gives the size of the red globules in various species accord- 

 ing to the measurements of Gulliver and Welcker : 



DIAMETER OF THE RED BLOOD-GLOBULES OF MAMMALIANS. 

 in Micro-Millimetres. 



Elephant . ... 9.20 Fox . .' 6.10 



Sloth .... 8.93 Ox . ... 5.95 



Ape .... 7.35 Horse . . . 5.43 



Dog .... 7.30 Sheep . . . 5.00 



Wolf .... 6.94 Red deer . . . 5.00 



Rabbit . . . . 6.90 Goat . , . 4.10 



Cat .... 6.50 Musk deer . . 2.50 



In animals where the red globules are small, they are proportionately 

 numerous. It is estimated by Kolliker that the mass of all the red 



