822 PHYSIOLOGY 



results according to the animal employed. In the case of the oxyhaemo- 



globin of the dog Jaquet obtained the following figures : 



In 100 parts 



C . . . 53-91 .. 54-97 



H 



N 

 Fe 



S 



o 



6-62 . . 7-22 



15-98 . . 16-38 



0-333 . . 0-336 



0-54 . . 0-568 



22-62 20-93 



The chief differences between different animals appear to have re- 

 lation to" the sulphur. Haemoglobin from the hen contains 0-857 per cent, 

 sulphur. All specimens are alike in containing a constant proportion of 

 iron, as is shown in the following Table : 



Oxyhsemoglobin of Fe per cent. Authority 



Dog 0-336 . . Jaquet. 



Horse 0-335 .. Zinoffsky. 



Ox 0-336 . . Hiifner. 



Hen . 0-336 . . Jaquet. 



On the assumption that each molecule of oxyhaemoglobin contains one 

 atom of iron, its molecular weight would be 16,660, and this result is borne 

 out by the volume of oxygen or carbonic oxide which can enter into combina- 

 tion with haemoglobin. It has been suggested by Bunge that the enormous 

 size of the haemoglobin molecule finds a teleological explanation ; if we 

 consider that iron is eight times as heavy as water, a compound which would 

 float easily along with the blood-current through the vessels could only be 

 secured by the iron being taken up by so large an organic molecule. Oxy- 

 haemoglobin is a compound in definite proportions of oxygen and haemo- 

 globin or reduced haemoglobin. It can be easily dissociated and is split up by 

 such simple means as exposure to a vacuum. If, for instance, some arterial 

 blood or solution of oxyhaemoglobin be introduced into a Torricellian 

 vacuum, the fluid is seen to give off bubbles of gas, and the colour changes 

 from a brilliant scarlet to a dull bluish red. In this process each gramme of 

 oxyhaemoglobin gives off 1'34 c.c. of oxygen. The same change can be 

 effected by treating a solution of oxyhaemoglobin with reducing agents such 

 as an alkaline solution of ferrous tartrate (Stokes's fluid) or ammonium 

 sulphide ; in the latter case reduction is aided by gently warming the 

 solution. Another reagent of value for effecting the reduction of oxyhaemo- 

 globin is a solution of hydrazine. The oxygen in oxyhaemoglobin can be 

 replaced by equivalent quantities of other gases. Thus if carbon monoxide 

 gas be led through a solution of oxyhaemoglobin, oxygen is given off and its 

 place is taken by an equal volume of carbon monoxide with the formation of 

 a more stable compound, carbon monoxide haemoglobin. This body is only 

 dissociated with extreme slowness and is unaffected by the addition of 

 reducing agents. By using special precautions to prevent oxidation of the 

 gas the carbon monoxide can be replaced in this compound by nitric oxide, 



