THE PRINCIPLES OF VENTILATION 315 



the injection of a trace of each other's protein. According to those 

 who study the phenomena of anaphylaxis, no such sensitivity can be 

 shown. If rats and guinea-pigs be confined together for one or two 

 months under the worst possible conditions of ventilation, the guinea- 

 pigs subsequently show no signs of anaphylactic symptoms when 

 injected with a small dose of rat's serum. 



It has been claimed that if rabbits be arranged in a series of 

 chambers, with the air led from one chamber to another, so that 

 each succeeding chamber received the vitiated air from the one 

 before it, the animals in the end cage died; but if the air received 

 into this cage were passed through sulphuric acid the rabbits 

 remained alive. 



These experiments also have been repeated with the greatest care 

 by several workers. It has been proved conclusively that no harm 

 results so long as a sufficient air-current is maintained to keep the 

 carbonic acid below a poisonous amount. The animal in the last 

 cage dies when the C0 2 reaches 10 to 12 per cent. If the C0 2 is kept 

 down, the animal in the last cage puts on weight and thrives as well 

 -as the animal in the first cage. Of course, it is necessary in such 

 experiments to clean the chambers daily, and supply the animals with 

 suitable food and bedding. 



A man can live many days in a closed chamber in comfort without 

 damage to his health, having not the slightest cognizance of any defect 

 in ventilation, when the ventilation is so reduced that the carbonic 

 acid accumulates in the chamber up to 1 per cent. that is to say, so 

 long as the air in the chamber is kept cool and dry. Eight students 

 were enclosed in a small chamber holding about 3 cubic metres of 

 air, and kept therein until the C0 2 has reached 3 to 4 per cent., and 

 the oxygen has fallen to 17 or 16 per cent. Unaware that the 

 oxygen was insufficient to support combustion they were puzzled to 

 find they could not light a cigarette. The wet-bulb temperature 

 rose meanwhile to about 85 F., the dry-bulb a degree or two higher. 

 Their discomfort became great, but this was relieved to an astonish- 

 ing extent by putting on electric fans placed in the roof, whirling 

 the air in the chamber, and so coding their bodies. 



In a crowded room, the air confined between the bodies and clothes 

 of the people is almost warmed up to body temperature and saturated 

 with moisture, so that cooling of the body by radiation, convection 

 by evaporation, becomes almost impossible. ThU leads to sweating, 

 wetness, and flushing of the skin, and a rise of sMn temperature. 

 The blood is sent to the skin, and stagnates there instead of passing 

 in ample volume through the brain and viscera. Hence arise the 

 feelings of discomfort and fatigue. The fans in the experiment 

 mentioned above whirled away the blanket of stationary wet air round 

 their bodies, and brought to the students the somewhat cooler and 

 drier air in the rest of the chamber, and so relieved the heat stagna- 

 tion from which they suffered. The relief became far greater when 

 cold water was circulated through a radiator placed m the chamber, 

 And so cooled the air of the chamber about 10 F. ' 



