THE USE OF PNEUMATIC CHAMBERS 221 



THE RESULTS OBTAINED BY THE USE OF PNEUMATIC CHAMBERS 



Boyle observed a bubble of gas in the aqueous humour of a 

 viper produced by the rapid evacuation of his air-pump. Such 

 an evolution can never take place in the comparatively slow ascent 

 of the balloonist. Laghi (1757) placed a bird, a cat, and a candle 

 under a bell-glass the animals lived long' after the candle nickered 

 out. Cigna (1760) put a sparrow under the bell of an air pump 

 and lowered the pressure to about 229 mm. Hg (8840 m.). He 

 renewed the air occasionally. The bird was none the worse after 

 30'. When an animal is killed under the air-pump it gives some 

 signs of restlessness, then falls over and dies with a few convulsive 

 movements. Death takes place inevitably, when the oxygen is 

 lowered to 3 per cent, of an atmosphere. In the deoxygenated air 

 of foul wells men suddenly, and without warning, fall unconscious. 



In a pneumatic chamber enriched with oxygen Bert exposed 

 himself to 240 mm. Hg (the height of Mount Everest). Mosso 

 exposed himself in 25' to 340 mm. Hg (6400 m.) and felt a heaviness 

 of the head, and found difficulty in counting his pulse, which rose 

 from 70 to 88. Recovering in 20' from these symptoms he exposed 

 himself to 292 mm. Hg (7167 m.), and again became heavy and 

 apathetic. Oxygen was then let into the chamber, and his pulse 

 rate dropped to 64, but became too thready to feel at the wrist. 

 After the pressure had been lowered further to 192 mm. Hg, he 

 became too apathetic to pick up the pencil which he had dropped. 

 The air at this stage enriched by oxygen yielded 8' 14 per 

 cent. atm. 2 . 



U. Mosso lowered himself to 310 mm. Hg. His mental faculties 

 became blurred, he experienced difficulty in reading his watch, was 

 twice unable to count his pulse, his handwriting altered, and his 

 memory weakened. His eyes became dull and apathetic. 



At 330 mm. Hg monkeys observed by Mosso vomited and 

 became apathetic and unsteady on their legs. Warm-blooded 

 animals are, owing to their quick metabolism, far more sensitive 

 than cold, and a low temperature and rapid decompression favour 

 the onset of symptoms (Bert). Lack of 2 only produces dyspnoea 

 if sudden and intense. Loewy found his breathing volume per min. 

 to be 4-027 1. at 750 mm. ; 4'497 1. at 435 mm. ; and 5*556 1. at 360 

 mm., a trifling increase compared to that produced by C0 2 retention. 



