Medical Apparatuses 415 



But in a later work 5 he is a little more explicit in the description 

 of the phenomena. 



The effect of compressed air, he says, is marked by two chief 

 points: 



1. Compressed air acts upon the circulation by slackening it; and 

 while it lessens the number of heartbeats, it regularizes their rhythm. 



These phenomena, which are hardly noticeable in a normal state 

 of health and under the effect of short or incomplete experiments, 

 become very marked in case of inflammatory or feverish diseases, 

 provided that the experimental conditions are properly fulfilled and 

 sufficiently maintained .... 



2. Compressed air does not affect general heat production as air 

 with higher oxygen content would do; for far from stimulating this 

 function, as has been supposed through analogy, it moderates it, and 

 in certain cases even depresses it. 



This fact, which I stated with some hesitancy in 1838, has been 

 proved since then by new evidence. Not only does the use of the 

 compressed air treatment develop no unusual heat within the thorax, 

 but, on the contrary, it tends to produce a general sensation of cold, 

 even when the temperature within the apparatuses is higher than 

 that outside; and in some subjects in whom this chilly feeling is more 

 marked, we note that it increases with the length and the degree of 

 compression of the treatment. 



Better results are obtained at moderate pressures (% of an atmos- 

 phere) than at higher degrees (% of an atmosphere). 



However, Tabarie's note contains no theoretical explanation. 



The first attempts of Pravaz to apply compressed air treatments 

 to therapeutics date back to 1836. In 1837, 6 he began to publish 

 the result of his observations. He summarized his previous notes 

 and memoirs in the work which we are taking as our guide. 7 



His apparatus measured 9 cubic meters. The pressure used was 

 generally from 30 cm. to 35cm. Pravaz describes as follows the phe- 

 nomena displayed by the subjects of his experiments: 



In most of the subjects of good constitution and in a healthy 

 state, the arterial circulation does not show great modifications, no 

 doubt because the respiration which was sufficient for hematosis under 

 ordinary pressure keeps about the same rhythm in compressed air; 

 but this is not true when there is a morbid acceleration of the pulse; 

 then it drops considerably, except in a few exceptional cases which 

 will be discussed later. 



The congestion of the capillaries of the skin and the mucous 

 membranes is evidently decreased by the increase in pressure exerted 

 upon the periphery of the body. This effect becomes very apparent 

 upon the surface to which a vesicant is applied or the conjunctiva, 

 when the latter is red and inflamed. 



The stimulation of the digestive organs, noted by MM. Colladon 

 and Junod, is not always limited to producing a simple increase of 



