444 Messrs. L. Hill and M. Greenwood, Jun. [Jan. 16, 



sante n'est pas menacee quand on atteint des pressions allant jusqu'a 

 5 kg. 400." (9) 



Hersertt and his medical colleagues do not appear to have entered the 

 pressure chamber themselves, so that we are not in possession of an accurate 

 record of the subjective effects as noted by trained scientific observers. One 

 of our objects therefore has been to study in detail the subjective and 

 physiological changes induced by greatly increased barometric pressures; 

 another object has been the investigation of the respiratory exchange under 

 the same conditions. In the present memoir we shall communicate the 

 results already obtained. 



Part I. 



Our experiments have been carried out in a steel cylinder kindly placed 

 at our disposal by Messrs. Siebe and Gorman, the eminent firm of naval 

 engineers, to whom we are further indebted for much valuable assistance. 



This cylinder (vide photograph, p. 446) had a capacity of 42*2 cubic feet, 

 and was provided with a mattress, blanket, and pillows, enabling the subject 

 to adopt a comfortable attitude. Compression was effected by means of 

 a two-cylinder motor-driven pump, which could raise the pressure to 

 + 6 atmospheres in about 40 minutes. Two decompression taps were 

 provided, with fine bores, permitting very careful adjustment of the rate 

 of escape. The chamber was also fitted with electric light, bell, telephone, 

 and a thick glass observation window ; the latter, however, was subsequently 

 covered with a steel shutter for greater security. The pressure was measured 

 by a Bourdon spring gauge, which had been tested for correctness. We shall 

 now give an account of a typical experiment. The description is reproduced 

 from notes taken at the time : — 



Experiment II. 29.11.05. 



The subject* (M. G.) entered the chamber at 10.40 a.m. In order to avoid 

 any accumulation of C0 2) a constant ventilation at the rate of 25 litres per 

 minute was maintained. 



* The measurements, etc., etc., of the two subjects were : L. H., age 39, weight (in 

 clothes) 8?2 kilogrammes, height 1*81 metres, vital capacity 3500 c.c, tidal air 510 c.c. ; 

 M. G., age 25, weight 53 kilogrammes, height 1*65 metres, vital capacity 4000 c.c, tidal 

 air 300 c.c. Both were in good physical condition. 



