RELATION OF PHYSIOLOGY TO MEDICINE. 83 



of these gases, the soldier begins to present very danger- 

 ous symptoms. The colour of the lips and face becomes 

 either blue or leaden coloured : the pulse is rapid, and 

 may be feeble and irregular : the breathing is increased, 

 and a watery sputum is coughed up. At the same time 

 the senses become dulled, and coma may supervene. 



What is the meaning of this symptom-complex ? 

 Let us begin with the colour of the lips and skin. Evi- 

 dently the blood in thehi has no longer its ordinary 

 scarlet colour. This might be due to decomposition of 

 the haemoglobin by the poisonous gas, with formation of 

 methaemoglobin or other decomposition products. But 

 we can negative this theory very quickly by taking a 

 drop of the blood, diluting it with water, saturating with 

 carbon monoxide or coal-gas, and comparing the tint of 

 the solution with that of normal blood similarly treated. 

 The haemoglobin shows no trace of decomposition ; and 

 if it had occurred, the colour of the lips would have 

 changed immediately after the exposure to the gas, and 

 not many hours later. The colour of the lips is therefore 

 due to the presence of reduced haemoglobin, as in any 

 ordinary true cyanosis. 



This cyanosis might be due either to great slowing of 

 the circulation, or to deficient oxygenation of the blood 

 in the lungs. There is, however, usually no sign of the 

 cold skin and other evidences of great slowing of circula- 

 tion ; and in many cases the blood-pressure is still high, 

 along with great cyanosis. It is evident, therefore, 

 that the main cause of the cyanosis is deficient oxygena- 

 tion in the lungs, and this in spite of vigorous and rapid 

 breathing, which is evidently not prevented by contrac- 

 tion of bronchi. The cause of this deficient oxygenation 



