246 



THE EFFECTS OF DECOMPRESSION 



exposed too long, or oxygen-poisoning will result, and the circu- 

 latory and respiratory mechanisms will fail to bring about the 

 escape of the dissolved air from the lungs. 



J. J. R. Macleod and the writer placed a frog in a small steel 

 chamber which was connected with a cylinder of compressed air 

 and provided with two windows by which an arc light could be 

 passed through the chamber. The web of the frog was stretched 

 on a wire, and fixed so that the small blood-vessels in it could 



be seen by applying a 

 microscope fitted with an 

 inch objective to the out- 

 side of the window. We 

 raised the pressure to 20 

 atm. and could see no 

 difference in the capillary 

 circulation. After waiting 

 for ten minutes we sud- 

 denly decompressed the 

 animal, and then noted 

 first one or two and then 

 a number of air - bubbles 

 scurrying through the capil- 

 laries, until finally columns 

 of air filled the vessels and 

 the circulation ceased. On 

 reapplying the pressure the 

 gas-bubbles again went into 

 solution and the blood cir- 

 culated normally. The dissolved gas in the blood could escape 

 from the body without forming emboli provided we made the 

 decompression gradual. The whole process is exemplified by a 

 bottle of aerated water : if the cork in such a bottle be drawn, 

 the dissolved gas escapes as bubbles of froth ; if the cork be 

 again pushed into the bottle, the gas re-enters again into solution 

 and the fluid becomes quiet. 



A large pressure chamber provided with observation window, 

 electric light, air-pump, and other facilities provided by Messrs. 

 Siebe & Gorman, the well-known marine engineers, enabled us to 

 thoroughly study the effects of rapid and slow decompression. 

 The chamber was provided with a large tap, by means of which 





FIG. 16. Nitrogen Bubbles in Vessels of 

 Spinal Cord of Dog, a Kesult of rapid Decom- 

 pression (v. Schrotter). 



