Summary and Discussion 491 



Circulation. The decrease in the pulse rate is also a matter of 

 general observation; M. Bucquoy alone (page 374) has made a 

 contradictory statement. In highly compressed air, Pol and Watelle 

 observed the rate to fall from 80 to 50; the change is especially 

 great when there was an abnormal acceleration. On return to 

 ordinary pressure, the usual rate is restored. 



The pulse undergoes still other changes, in regard to which 

 the tracings of Vivenot give us definite information (Fig. 10-13, 

 pages 424, 425); its amplitude is much lessened, and it shows all 

 the characteristics of exaggerated arterial tension. 



No direct experiment has been made to measure in animals 

 the changes in the blood pressure and the speed of the blood flow. 



The capillary circulation is evidently much changed. The skin 

 and the mucous membranes grow pale, especially when they were 

 the seat of congestion or inflammation; in regard to this important 

 point in therapeutics, the observations of physicians are more con- 

 vincing than the experiments made by Vivenot on the ears of 

 white rabbits. 



The blood becomes a brilliant red in color; this has been ob- 

 served particularly in caisson workers. The venous blood drawn 

 from the arm, as Pol and Watelle were the first to note (page 367) , 

 looks as if it were arterial, a certain indication of the greater pro- 

 portion of oxygen which it contains: according to these authors, 

 this redness of the blood persists for some time. 



Secretions. The only important observation which has been 

 made concerns the increase in the urinary secretion; but no exact 

 measurement has been taken, and no analysis of the urine has been 

 made. 



Some observers have spoken of the dryness of the skin,- but it 

 is difficult to get exact estimates on this point. 



Nutrition. Very different estimates of the variations in the 

 weight of the body have been made by different authors. The 

 physicians of caisson workers and divers declare that there is a 

 loss of weight; those who used compressed air with a therapeutic 

 purpose consider that there is an increase in weight. Besides the 

 fact that there may be a great difference in this regard between 

 the effect of a pressure of 3 atmospheres and that of the pressure 

 of a few centimeters of mercury, one can hardly compare caisson 

 workers, men who are exhausted by their hard labor, who seek 

 dangerous assistance in alcoholic beverages, and who are generally 

 much undernourished, with subjects who are in excellent hygienic 

 conditions and who can satisfy completely the increased appetite 



