5<> THE CIRCULATING LIQUIDS OF THE 



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 per cent. ; 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. 



Hcemoglobin. 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- 

 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- 

 tent of almost exactly 

 one-third of i percent. , 

 and there is also a little 

 sulphur, the amount of 

 which stands in a very 

 simple relation to the quantity of iron (i atom of iron to 3 of sulphur 

 in dog's haemoglobin, and i atom of iron to 2 of sulphur in the haemo- 

 globin of the horse, ox, and pig). 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 758 H 12 o3N 195 S 3 FeO 218 , which would make 

 the molecular weight 16,669. Direct determinations of the molecular 

 weight gave 15,115 for oxyhaemoglobin of the horse, and 16,321 for that 

 of the ox'(Humer and Gansser). While these 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- 



Fig. 12. Diagram of Spectroscope. A, source of light; 

 B, layer of blood; C, collimator for rendering rays 

 parallel; D, prism; E, telescope. 



