1833.] On holding the Breath for a lengthened Period. 361 



happen in succession in cesspools, and similar cases, for want 

 of this precaution. 



It is hardly needful to say, do not try to breathe the air of 

 the place where help is required. Yet many persons fall in 

 consequence of forgetting this precaution. If the temptation 

 to breathe be at all given way to, the necessity increases, and 

 the helper himself is greatly endangered. Resist the tendency, 

 and retreat in time. 



Be careful to commence giving aid with the lungs full of air, 

 not empty. It may seem folly to urge this precaution, but I 

 have found so many persons who, on trying the experiment on 

 which the whole is based, have concluded the preparation by 

 closing the mouth and nostrils after an expiration, that I am 

 sure the precaution requires to be borne in mind. 



I have thought it quite needless to refer to the manner in 

 which the preparation enables a person to increase so con- 

 siderably the time during which he may suspend the operation 

 of breathing. It consists, of course, chiefly in laying up for 

 the time, in the cells of the lungs, a store of that vital principle 

 which is so essential to life. Those who are not aware of the 

 state of the air in the lungs during ordinary respiration, and 

 its great difference from that of the atmosphere, may obtain a 

 clearer notion from the following experiment. Fill a pint or 

 quart jar with water over the pneumatic trough, and with a 

 piece of tube and a forced expiration throw the air from the 

 lungs in their ordinary state into the jar ; it will be found that 

 a lighted taper put into that air will be immediately extinguished. 



A very curious fact connected with the time of holding the 

 breath was observed by Mr. Brunei, jun., and has, I think, 

 never been published. After the river had broken into the 

 tunnel at Rotherhithe, Mr. Brunei descended with a companion 

 (Mr. Gravatt, I think,) in a diving-bell, to examine the place : 

 at the depth of about 30 feet of water, the bell touched the 

 bottom of the river, and was over the hole ; covering it, but too 

 large to pass into it. Mr. Brunei, after attaching a rope to 

 himself, inspired deeply, and sunk, or was lowered through 

 the water, in the hole, that he might feel the frames with his 

 feet, and gain further knowledge, if possible, of the nature of 

 the leak. He remained so long beneath without giving any 

 signal, that his companion, alarmed, drew him up before he 



