314 A TEXTBOOK OF PHYSIOLOGY 



by it. While we naturally avoid any smell that excites disgust and 

 puts us off our appetite, yet the offensive quality of the smell does 

 not prove its poisonous nature. On descending into a sewer, after 

 the first ten minutes the nose ceases to smell the stench ; the air therein 

 is usually found to be far freer from bacteria than the air in a school- 

 room or tenement. 



If we turn to foodstuffs, we recognize that the smell of alcohol and 

 of Stilton or Camembert cheese is horrible to a child or dog, while the 

 smell of putrid fish the meal of the Siberian native excites no less 

 disgust in an epicure, who welcomes the cheese. Among the hardiest 

 and healthiest of men are the North Sea fishermen, who sleep in the 

 cabins of trawlers reeking with fish and oil, and for the sake of warmth 

 shut themselves up until the lamp may go out from want of oxygen. 

 The stench of such surroundings may effectually put the sensitive, 

 untrained brain-worker off his appetite, but the robust health of the 

 fisherman proves that this effect is nervous in origin, and not due to 

 a chemical organic poison in the air. 



The supposed existence of organic chemical poison in the expired 

 air is based upon experiments in which either the condensation water 

 obtained from the breath, or water which was used several times 

 over to wash out the trachea of dogs, was injected into guinea-pigs 

 and rabbits. The water was injected subcutaneously and in large 

 amounts, and produced signs of illness, collapse, and death. 



Such experiments have been repeated by many others, and Avith 

 negative results by those whose methods of work demand most respect. 

 A few confirmatory results have been obtained by methods of experi- 

 ment which are truly absurd in their conception: 1 to 2 c.c. of con- 

 densation water (obtained by breathing for many hours through a 

 cooled flask) have been injected into a mouse weighing 13 grammes 

 or so. This is equivalent to injecting 5 litres of water into a man 

 weighing 65 kilos. Who would not be made ill by the injection of 

 about 9 pints of cold water beneath his skin ? It has been shown 

 that injections of pure water alone in doses of over 1 c.c. may make a 

 mouse ill. 



In the washings of a dog's trachea, or the condensation fluid obtained 

 from the breath, there is bound to be present traces of the proteins of 

 the saliva. A second injection of such into the~same animal might 

 produce " anaphylactic shock" (see p. 111). Experiments have been 

 published which seem to show that guinea-pigs can be sensitized by the 

 injection of the condensation water of human breath, so that aiiaphy- 

 laxis is produced in these pigs by a subsequent injection of a trace of 

 human serum. Owing to the method employed, it seems certain that 

 saliva must have contaminated the condensation water. The guinea- 

 pigs therefore became sensitized to human protein by the injection of 

 the condensation water containing traces of salivary protein. Such 

 results, it is claimed, afford evidence in favour of the exhalation of 

 a volatile protein an organic chemical poison. If there were any- 

 thing in these claims, we should expect to find rats, which dwell in 

 the same confined cage and breathe each other's breath, sensitive to 



