Chapter III 



THEORETICAL EXPLANATIONS AND 

 EXPERIMENTS 



Even if the experiments and the theories which we reviewed in 

 speaking of the effect of diminished pressure were numerous, 

 varied, contradictory, sometimes strange and almost incompre- 

 hensible, at least their purpose was to answer a single question: 

 What is the cause of the symptoms of decompression? It is other- 

 wise with those which we shall summarize in the present chapter, 

 and their discussion will necessarily betray the confusion into 

 which those who expressed them have fallen. 



The data which we have hitherto reported show that in truth 

 the phenomena displayed by persons subjected to the effect of 

 compressed air are extremely varied and appear under conditions 

 which can hardly be compared, perhaps are absolutely unlike. In 

 fact, we must take account, at least when the compression has 

 risen to a certain degree, not only of the phase of compression but 

 also of that of decompression, the dangerous effects of which were 

 soon shown by observations made by the workmen themselves. 

 It was these effects which first attracted attention by their strange- 

 ness and their severity. The changes which the compressed air 

 itself causes in the different physiological functions' are not very 

 great, within the limits hitherto observed, and to verify them 

 attentive and sustained observation was required, aided by the in- 

 strumental resources used today by physiology and pathology. Some 

 physicians have distinguished between the two classes of phe- 

 nomena, and have tried to explain them by different reasons; but 

 others have confused them in common theories, so that it would 

 not be possible to subdivide this chapter, as personally we should 

 like to do. 



Let us add that laboratory experiments on animals have been 



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