THE FORMED CONSTITUENTS OF THE BLOOD 



151 



the blood of a man there is found 13.8 per cent hemoglobin, and in that of a 

 woman 12.6 per cent. 



The quantity of haemoglobin in the blood shows great variations under 

 different circumstances, and as a rule, though not always, it varies directly 

 as the number of corpuscles. The quantity of 

 haemoglobin in proportion to the body weight is 

 greatest in the newborn and sinks rapidly during 

 the first few days after birth e. g., in the rabbit 

 in twenty- two days, it sinks from about 13 g. to 

 4 g. per kg. of body weight. During this time 

 the absolute quantity of haemoglobin increases 

 and the iron stored up in the body in other 

 forms decreases (Abderhalden). 



Oxyhaemoglobin crystallizes out of its solu- 

 tion more or less readily. The crystals ( Fig. 46 ) 

 are blood red, are transparent, and belong, what- 

 ever their form, to the rhombic system (Lang). 

 From fresh human blood one may obtain three 

 forms of crystals, namely: (1) large, scalari- 

 form plates, (2) sharply defined, dark red, doubly 

 refractive, four-angled prisms, and (3) sharply 

 defined rods much split up at the ends (Frie- 

 boes). Only the oxyhaemoglobin of the squirrel 

 (Fig. 46 c) crystallizes in six-sided tablets of the 

 hexagonal system. 



Haemoglobin is distinguished from oxyhaemo- 

 globin chiefly by being more easily soluble, and 

 more difficult of crystallization, although the two 

 are as a rule isomorphic. The crystals and the 

 water solution of haemoglobin are darker, more 

 violet, or purple colored than the crystals and 

 the solution of oxyhsemoglobin. In thin layers 

 haemoglobin is greenish, in thicker layers red. 

 Oxyhaemoglobin solutions are always red what- 

 ever the thickness. Finally, the two show note- 

 worthy differences in their absorption spectra, 

 as will be evident from Figs. 47 and 48. If 

 the solution is not too concentrated the absorp- 

 tion spectrum of oxyhaemoglobin shows two 

 bands a and ft between the D and E lines. 

 With weaker solutions the ft band disappears 

 first. The more concentrated the solution is, 

 however, the broader the bands become until 

 finally they fuse together, whereby the blue and 

 the violet parts of the spectrum are at the same time more and more obscured. 

 The absorption spectrum of haemoglobin on the contrary shows a single broad 

 band between the D and E lines, but nearer the D. 



In methcemoglobin oxygen occurs in the same quantity as in oxyhaemo- 



