1 58 HANDBOOK OF PHYSIOLOGY. 



must be adopted, e.g., the addition of alcohol, ether, or chloroform, rapid 

 freezing, and then thawing, an electric current, a temperature of 60 C. 

 (140 F.), the addition of sodium sulphate, or the addition of decom- 

 posing serum of another animal. 



The haemoglobin of human blood crystallizes with difficulty, as does 

 also that of the ox, the pig, the sheep, and the rabbit. 



The forms of hemoglobin crystals, as will be seen from the appended 

 figures, differ greatly. 



Haemoglobin crystals are soluble in water. Both the crystals them- 

 selves and also their solutions have the characteristic color of arterial 



blood. 



A dilute solution of oxy-haemoglobin gives a characteristic appear- 

 ance with the spectroscope. Two absorption bands are seen between 



Fig. 135. Crystals of oxy-haemoglobin Fig. 136. Oxy-haemoglobin crystals tetra- 

 prismatic, from human blood. heclral, from blood of the guinea-pig. 



the solar lines D * (which is the sodium band in the yellow) and E * (see 

 plate), one in the yellow, with its middle line some little way to the right 

 of D, is very intense, but narrower than the other, which lies in the 

 green near to the left of E. Each band is darkest in the middle and 

 fades away at the sides. As the strength of the solution increases the 

 bands become broader and deeper, and both the red and the blue ends 

 of the spectrum become encroached upon until the bands coalesce to 

 form one very broad band, aod only a slight amount of the green re- 

 mains unabsorbed, and part of the red; on still further increase of 

 strength the former disappears. 



If the crystals of oxy-haemoglobin be subjected to a mercurial air- 

 pump they give off a definite amount of oxygen (1 gramme giving off 

 1.59 ccm. of oyxgen), and they become of a purple color; and a solution 

 of oxy-haemoglobin may be made to give up oxygen, and to become pur- 

 ple in a similar manner. 



* These letters refer to " Fraunhofer's" lines. 



