414 Historical 



lessens and may even be entirely obliterated; so that the blood, on 

 its return towards the heart, follows the deep veins. If the caliber 

 of the superficial vessels increases or diminishes because of the tension 

 of the atmospheric elasticity, the same thing must be true in the pul- 

 monary organs, which are under the same conditions in this respect; 

 the inevitable result of this must be that when the pressure of the 

 air is increased, the quantity of venous blood contained in the lungs 

 must decrease; no doubt that is why a much greater quantity of air 

 can be inhaled at each inspiration than at normal atmospheric 

 pressure. 



If the increasing density of the air lessens the caliber of the 

 venous vessels, the necessary result must be that the blood flows in 

 greater quantity in the arterial system, and towards the principal 

 nervous centers, especially in the brain, which is protected from the 

 direct pressure of the atmosphere by the resistance of the bony case 

 in which it is contained. So the functions of the brain are activated, 

 the imagination is lively, thoughts have a peculiar charm, and in some 

 persons symptoms of intoxication are evident. This increase of inner- 

 vation acts also upon the muscular system; movements are easier 

 and more assured. 



4. The functions of the alimentary canal are expedited: thirst 

 is wanting; 



5. The salivary and renal glands secrete their fluids abundantly. 

 (P. 159.) 



The report made by Magendie on the work of M. Junod, from 

 which we quoted earlier (page 229) the part relating to the effect 

 of decrease in atmospheric pressure, says nothing new on the sub- 

 ject, about either symptoms or theories. 



It was not until 1838 that Tabarie 4 published his researches, 

 which, he said then, nevertheless dated back to a considerably 

 earlier period. 



His note ^hows that he had planned a series of very complex 

 problems, since the processes which he had used included: 



1. General compression of the air over the whole body; 



2. Local compression over the limbs; 



3. Local rarefaction over the limbs. 



4. Alternate and local compression and rarefaction or oscillation 

 on the limbs; 



5. Rarefaction over the whole body except the head; 



6. Use of alternate compressions and rarefactions over the whole 

 body except the mouth, resulting in an artificial and complete respir- 

 ation to be used in cases of asphyxia. 



The rest of his note contains only a very short summary of 

 applications of these different methods. It contains nothing definite 

 either in regard to physiological phenomena or relating to the 

 theoretical ideas he formed about the action of compressed air. 



