APPENDIX — RESPIRATORY CHANGES IN BLOOD. 647 



it cannot be driven out by carbonic oxide, they do not prevent 

 its removal by reducing agents. These first break up the 

 nitrite compound, and then deoxidise the haemoglobin ; and 

 when this is next exposed to air, it takes up oxygen in the 

 normal way. On this account, the action of nitrites in 

 impeding or arresting internal respiration is only transitory ; 

 for, when the blood on which they have acted once becomes 

 deoxidised during its passage through the capillaries, it is 

 restored to its normal condition. The action of carbonic 

 oxide, on the contrary, is permanent, the blood with which 

 it has combined remaining unaltered during its circulation 

 either through the body or the lungs ; and, if the greatest part 

 of the haemoglobin have been acted upon, life can only be 

 saved by the transfusion of fresh blood into the vessels, 

 although, in slighter cases, a fatal issue may be averted by the 

 dilig nt use of artificial respiration. Internal respiration is 

 also diminished by phosphorus; and the fatty degeneration 

 produced by this substance has been shown by Voit and 

 Bauer to be partly due to this action. It is not due to this 

 alone, however, for the phosphorus has a double action: 1. It 

 causes the albuminous tissues to split up more rapidly ; 

 2. It lessens the combustion of the products of decomposition. 

 The increased rapidity of albuminous decomposition causes 

 more urea to appear in the urine; and, if the nitrogenous 

 compounds be not sufficiently oxidised, leucin and tyrosine 

 may appear instead of urea. Fat is also formed from alljumen 

 more rapidly, as well as more slowly oxidised, than in the 

 normal condition. 



In order to ascertain whether the haemoglobin of the blood 

 has been altered by the action of a drug : 1. If it be poisonous, 

 examine the blood from the arteries and veins of an animal 

 which has been poisoned by it, and note whether its colour 

 is normal in both sets of vessels or not. 2. Dilute a portion 

 of this blood with water, examine it with the spectroscope, and 

 see what spectrum it presents. Shake it with air, and observe 

 if the bands of oxyhaemoglobin alone are present, and if they 

 are of their normal intensity and in their normal place. Take 

 another portion of the diluted blood and add to it a deoxidis- 



