280 



THE BLOOD. 



The hemoglobin of some animals, as the guinea-pig, cat, and 

 dog, crystallizes very readily, while that of man, and the mammals 

 generally, forms crystals with more difficulty. To obtain crystals of 

 oxy hemoglobin, the blood should be mixed in a test-tube with one- 

 sixteenth its volume of ether and the tube shaken with consid- 

 erable force. The coloring-matter passes into the plasma, and the 

 blood becomes lakey. If the tube is then placed on ice, in a short 

 time the crystals will form and can be examined under the micro- 

 scope. The form of the crys- 

 tals varies in different animals 

 (Fig. 150). In the guinea-pig, 

 the blood of which is easily 

 obtained, and whose oxyhe- 

 moglobin crystallizes readily, 

 they are rhombic tetrahedra. 

 Derivatives of Hemoglobin. 

 Besides oxyhemoglobin, the 

 properties of which have al- 

 ready been given, there are 

 various derivatives of hemo- 

 globin ; among them are the 

 following : 



Carbon-monoxid Hemoglo- 

 bin. As one molecule of 

 hemoglobin combined with 

 one of oxygen forms oxyhem- 

 oglobin, so one* molecule of 

 hemoglobin united with one 

 of carbon monoxid forms 

 Carbon-monoxid hemoglobin. 

 There is, however, one strik- 

 ing difference in the two com- 

 binations. In the former the 

 oxygen is readily displaceable, 

 while in the latter the com- 

 pound is a very stable one, 

 although Gamgee has shown 

 that by the long-continued passage of neutral gases through solu- 

 tions of CO-hemoglobin the CO is gradually driven out, and reduced 

 hemoglobin is obtained. Carbon monoxid is the gas formed when 

 combustion is incomplete, such as is produced by the charcoal fur- 

 nace used in France for suicidal purposes ; the charcoal fumes when 

 inhaled in sufficient quantity produce fatal results. It is also a con- 

 stituent of illuminating-gas, where it exists in proportions ranging 

 from 7.9 to 28.25 per cent., and is not infrequently the cause of 

 death. The gas displaces the oxygen and unites so firmly with the 

 hemoglobin that even with artificial respiration it cannot be dis- 



FIG. 150. Crystallized hemoglobin: a, 6, 

 crystals from venous blood of man ; c, from 

 the blood of a cat ; d, from the blood of a 

 guinea-pig ; e, from the blood of a hamster ; 

 /, from the blood of a squirrel (after Frey). 



