Hitman Physiology. 185 



-whole current of the blood becomes tainted with the morbid 

 products of an unnatural nu&rition. All animals, in a state of 

 nature, seem able to choose their proper food, and to avoid 

 poisons. 



Smell resides wholly in some large nerves spread over the 

 inner surface of the nasal cavities. We draw in with our breath 

 floating atoms of various bodies, odours ; and a sense of their 

 qualities are conveyed by these nerves to the brain and the 

 mind. It is true that we also taste some strong odours; the 

 molecules entering with the breath are caught by the tongue, 

 and make their impression as a savour on the nerves of taste. 

 But taste, smell, and all the senses are only modifications of 

 the sense of touch or feeling. The atmosphere is filled with 

 odorous substances the vapour of the essential oils of plants 

 and flowers, the various emanations of insects and animals, gases 

 that rise from decaying vegetable and animal substances, the 

 smoke of coal, wood, and burning refuse, or from metal and 

 chemical works, and worst of all, the stench of human filth and 

 disease. Most great towns are full of stenches; the country, 

 on the contrary, when not infected with nuisances of human 

 production, is full of delightful odours. What more charming 

 than a ride or drive among flowering bean fields, lime trees, 

 apple blossoms, and meadows of new mown hay ! 



The sense of smell not only guards the mouth and forbids 

 the introduction of unfit food, putrid, nauseous, or acrid matters, 

 but it guards still more, perhaps, the lungs from inhaling foul 

 or poisoned air. It warns us against entering crowded and 

 ill-ventilated rooms, breathing noxious gases, inhaling the odours 

 of putrifying substances, and from remaining in the vicinity of 

 those who are neglectful of personal cleanliness. Strong per- 

 fumes, snuff, and tobacco smoke, injure this sense and its 

 protective powers. If our senses were in their natural condi- 

 tion, we should probably be able to avoid nearly all the causes 

 of disease in malarias and contagions. 



