BIOLOGY. 283 



proval of Dr. Jaminet. Those most severely affected were sent 

 to the city hospital, and had the benefit of the advice and treat- 

 ment of its resident physician, Prof. E. A. Clark. 



The total number of men employed in the air-chamber of this 

 pier was 352. Of this number, about 30 were seriously affected. 

 Notwithstanding the care and skill with which those most severe- 

 ly attacked were treated, 12 of the cases proved fatal. Each one 

 of these, without exception, I believe, was made the subject of 

 careful inquest by the coroner, aided by an autopsy conducted 

 usually by some of our most skilful surgeons and physicians. 



Whilst the exciting- cause in all of these cases was doubtless 

 the exposure of the system to the pressure of the condensed air 

 of the chamber, the habits and condition of several of those who 

 died were, at the time they went to work, such as would have ex- 

 cluded them from it if subjected to the examination of Dr. Jami- 

 net, and the verdict in about one-half of the cases gave a totally 

 different cause for the death of the patient. Nearly or quite all 

 of these deaths happened to men unaccustomed to the work ; 

 several of them to men who had worked but 1 watch of 2 hours. 

 In contrast to this, is the fact that quite a large number of the 

 men (certainly one-half of those constantly employed) com- 

 menced with the work at its inception, and remained throughout 

 its continuance entirely without injury or inconvenience. 



The gentlemen composing the engineer corps of the bridge all 

 visited the air-chamber, some of them quite often, either in the 

 discharge of their professional duties, or from motives of curios- 

 ity, and none of them suffered any injury whatever. 



Much diversity of opinion was expressed by the medical gentle- 

 men who investigated the symptoms and held autopsies of the 

 deceased. Some of these gentlemen maintained that a slower 

 transition from the abnormal to the natural pressure would have 

 been less injurious; others claimed, on the contrary, that it was 

 from the too rapid application of pressure in passing from the 

 natural into the compressed air. The fact that the air-lock tend- 

 ers were in no case affected, although subjected many times 

 during a watch of 2 hours in the air-lock to rapidly alternating 

 conditions of the atmosphere, at one moment in its "normal state 

 in the lock, and 5 minutes later exerting a pressure of 50 pounds 

 per square inch upon every part of the body, would seem to prove 

 both of these theories unsound, and lead us to believe that in the 

 length of time to which the human system is subjected to this 

 extraordinary pressure exists the real source of danger, and not 

 from any rapid alternations of pressure to which it is exposed. 



After the caisson reached the rock, I have frequently, when 

 passing through the air-lock, admitted the compressed air into it 

 so quickly that none but those well accustomed to it could relieve 

 the pressure upon their ears, and yet I felt no ill effects whatever 

 from this rapidly increased pressure ; and in going out I have let 

 the pressure off so fast that the temperature in the lock has fallen 

 32 degrees (F.) in consequence. These transitions occupied but 

 3 or 4 minutes. 



The fact that the air-chamber was briefly visited by thousands 



