3 S8 TEE POPULAR SCIENCE MONTHLY 



C0 2 is kept below 2 to 3 per cent, they are capable of carrying out 

 efficient work. In the case of workers in compressed air it is impor- 

 tant to bear in mind that the effect of the C0 2 on the breathing depends 

 on the partial pressure and not on the percentage of this gas in the 

 air breathed. 



By a series of observations made on rats confined in cages fitted 

 with small, ill-ventilated sleeping chambers, we have found that the 

 temperature and humidity of the air — not the percentage of carbon 

 dioxide or oxygen — determines whether the animals stay inside the 

 sleeping room or come outside. When the air is cold, they like to 

 stay inside, even when the carbon dioxide rises to 4 to 5 per cent, of 

 an atmosphere. When the sleeping chamber is made too hot and moist 

 they come outside. 



The sanitarian says it is necessary to keep the C0 2 below 0.01 per 

 cent., so that the organic poisons may not collect to a harmful extent. 

 The evil smell of crowded rooms is accepted as unequivocal evidence of 

 the existence of such. He pays much attention to this and little or 

 none to the heat and moisture of the air. The smell arises from the 

 secretions of the skin, soiled clothes, etc. The smell is only sensed by 

 and excites disgust in one who comes to it from the outside air. He 

 who is inside and helps to make the " fugg " is both wholly unaware 

 of and unaffected by it. Fliigge points out, with justice, that 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 poison- 

 ous nature. For the smell of the trade or food of one man may be hor- 

 rible and loathsome to another not used to such. 



The sight of a slaughterer and the smell of dead meat may be 

 loathly to the sensitive poet, but the slaughterer is none the less 

 healthy. The clang and jar of an engineer's workshop may be unen- 

 durable to a highly strung artist or author, but the artificers miss the 

 stoppage of the noisy clatter. The stench of glue-works, fried-fish 

 shops, soap and bone-manure works, middens, sewers, become as nothing 

 to those engaged in such, and the lives of the workers are in no wise 

 shortened by the stench they endure. The nose ceases to respond to 

 the uniformity of the impulse, and the stench clearly does not betoken 

 in any of these cases the existence of a chemical organic poison. 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, 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 



