BLOOD. 1(11 



1 . The general physiological chemistry of the blood. 



General physical relations of the blood. 



The blood, while moving in the living body, consists princi- 

 pally of a nearly colourless fluid, in which the blood-corpuscles 

 are swimming ; in consequence, however, of these coi-puscles 

 being too minute to be distinguished by the naked eye, it 

 appeal's, among the higher classes of animals, as an opaque 

 and intensely red fluid. 



In the majority of the lower (invertebrate) animals, the 

 blood is white ; it is however red in the annelida, colourless in 

 most of the mollusca, but in manv of the snails of a milk-white 

 colour; in the Helix pomatia of a sky-blue, and in the Pla- 

 norbis corneus, of a dark amethyst colour. In the dorsal 

 vessels of insects it is usually transparent, and of diff"erent 

 colours ; it is, for instance, green in the Orthoptera, yellow in 

 the silkworm, orange in the caterpillar of the willow-moth, 

 and of a dark brown colour in most of the beetles. i The 

 blood-corpuscles of red blood contain within their coat, or 

 shell, a fluid impregnated with globuKn and hsematin, and a 

 nucleus, which may be easily recognized in the larger cor- 

 puscles. 



The blood of the mammalia is a somewhat thick, viscid 

 fluid, with a specific gravity which varies, according to dif- 

 ferent authors, from 1041 to 1082. In a large number of 

 experiments made upon the blood of man, the ox, and the 

 horse, I found it to be between 1051 and 1058. The average 

 was 1042, which corresponds ver}^ nearly with the statement 

 of Berzelius. 



[The average specific gravity of human blood may be fixed 

 at 1055 according to Nasse,^ and at 1056 according to Zim- 

 mermann.^ The blood of man is always thicker, and at least 

 one thousandth hea\'ier than that of woman ; in a state of 

 health it is always above 1053 in man, while in woman it is 

 frequently not above 1050. Robust men will not unfre- 

 quently yield blood of spec. grav. 1058 or even 1059, while in 

 pregnant women the specific gravity is sometimes as low as 



' Burdach's Physiologic. 



2 Article ' Blut,' in Wagner's Handworterbucli, vol. 1, p. 82. 



3 Hufeland's Journal, 1843. 



