5<> THE CIRCULATING LIQUIDS OF THE BODY 



The Coloured Corpuscles consist of rather less than 60 per cent, of 

 water and rather more than 40 per cent, of solids. Of the solids the 

 pigment haemoglobin makes up about 90 per cent. ; the proteins and 

 nucleo-protein of the stroma about 7 percent.; lecithin and choles- 

 terin 2 to 3 per cent. ; inorganic salts (which vary greatly in their 

 relative proportions in different animals, but in man consist chiefly 

 of phosphates and chloride of potassium, with a much smaller 

 amount of sodium chloride) about i per cent. Potassium has been 

 demonstrated microchemically in frog's erythrocytes (Macallum) 

 (Frontispiece] . There is evidence that a portion of the salts is more 

 firmly combined than the rest, so that, even after the action of the 

 most energetic laking agents, this fraction remains attached to the 

 stroma. The erythrocytes of some animals e.g., the dog contain 

 dextrose. When dextrose -is added to human blood it rapidly dis- 

 tributes itself over corpuscles and plasma (Rona), although not 

 exactly in proportion to their respective volumes (Masing). Hither- 

 to the dextrose in blood has been reckoned as if it all belonged to the 

 plasma. 



Hemoglobin. Of all the solid constituents of the blood, haemoglobin 

 is present in greatest amount, constituting as it does no less than 

 13 per cent., by weight, of that liquid. It is an exceedingly complex 



body, containing car- 

 D c bon, hydrogen, nitro- 



WA gen, and oxygen in 



much the same pro- 

 portions in which they 

 exist in ordinary pro- 

 teins (p. i). Iron is 

 also present to the ex- 

 Pig. 12. Diagram of Spectroscope. A, source of light ; tent f almost exactly 

 B, layer of blaod; C, collimator for rendering rays one-third pi I percent., 

 parallel ; D, prism ; E, telescope. an <3 there is alsoa little 



sulphur. Haemoglobin 



is made up of a protein element which contains all the sulphur and a 

 pigment which contains all the iron, the protein constituting by far 

 the larger portion of the gigantic molecule, whose weight has been 

 estimated at more than 16,000 times that of a molecule of hydrogen. 

 Since its percentage composition is still undetermined with absolute 

 precision, it is impossible to give an empirical formula that is more 

 than approximately correct. For dog's haemoglobin Jaquet gives 

 C-58 H i203 N i95 S 3 FeO 2i8- which would make the molecular weight 16,669. 

 Direct determinations of the molecular weight gave 15,115 for 

 oxyhsemoglobin of the horse, and 16,321 for that of the ox (Hiifner and 

 Gansser). Whilethese numbers need not be taken as more than a rough 

 approximation, they at least show that the haemoglobin molecule is an 

 exceedingly large one. 



The most remarkable property of haemoglobin is its power of 

 combining loosely with oxygen when exposed to an atmosphere con- 

 taining it, and of again giving it up in the presence of oxidizable 

 substances or in an atmosphere in which the partial pressure of 

 oxygen (pp. 248-253) has been reduced below a certain limit. It 



