32 A Manual of Veterinary Physiology. 



doing- with considerable facility, it is spoken of as reduced 

 haemoglobin. These, therefore, are its two conditions of 

 oxidation: as oxy-haemoglobin it is charged in the capil- 

 laries of the lungs, brought back to the heart and dis- 

 tributed all over the body ; as partly reduced haemoglobin 

 it is produced in the tissues, and brought back by the veins 

 to the heart for distribution to the lungs, where it renews 

 its oxidized condition. Haemoglobin is never completely 

 reduced in the body, excepting in the last stage of 

 asphyxia. 



Oxy-hainoglobin crystallizes in some animals, hare and 

 guinea-pig, with facility ; with others, ox, sheep, and pig, 

 with difficulty. The crystals are generally rhombic plates 

 and prisms ; but the form differs according to the animal. 

 Reduced haemoglobin does not crystallize. 



The two haemoglobins produce quite distinctive spectra 

 when examined by the spectroscope, by which they may be 

 readily recognised. To put the matter roughly, oxy- 

 hsemoglobin gives a well-marked double band in the green 

 portion of the spectrum, one band being wide the other 

 narrow; whilst reduced haemoglobin gives one wide single 

 band in the same position. 



Oxygen and haemoglobin are so lightly bound together 

 that they are readily separated. The oxygen is given off if 

 the blood be placed in a vacuum or boiled, or if it be brought 

 in contact with indifferent gases— such as nitrogen and 

 hydrogen. It is the facility with which haemoglobin parts 

 with its oxygen which enables the tissues to obtain it. 



Haemoglobin forms, according to some observers, three, 

 according to others four, compounds with gases : 



With oxygen it forms oxy-haemoglobin and methsemoglobin. 

 „ carbonic oxide it forms CO haemoglobin. 

 „ nitric oxide „ KO „ 



Oxy-fuemoglobin we have dealt with : the others, in a 

 work of this kind, can only receive a short notice at our 

 hands, though the subject is one which is full of interest. 



Methsomoglobin is produced by allowing blood to be ex- 



