453 



tained and a series of deductions, applicable especially to the solution 

 or elucidation of hygienic questions. From the former the following 

 facts are extracted : 



The total quantity of air inspired in 24 hours (allowance being 

 made for intervals amounting altogether to 40 minutes, during 

 which it was not recorded) was 711,060 cub. ins. ; or an average of 

 29,627 cub. ins. per hour and 493'6 per minute. The quantity was 

 much less during the night than during the day. There was an 

 increase as the morning advanced and a decrease at about 8 h 30' P.M., 

 but most suddenly at about 11 P.M. During the day the quantity 

 increased immediately after a meal, and then subsided before the 

 next meal ; but in every instance it rose again immediately before a 

 meal. The rate of frequency of respiration generally corresponded 

 with the quantity, but the extremes of the day and night rates were 

 greater. The period of greatest parallelism was between tea and 

 supper. An increase was occasioned by one meal only, namely break- 

 fast. The average depth of respiration was 26'5 cub. ins., with a 

 minimum of 18' 1 cub. ins. in the night, and a maximum of 32-2 cub. 

 ins. at l h 30' P.M. The mean rate of the pulse was 76 per minute, 

 the minimum at 3 1 ' 30' A.M., the maximum at 8 h 45' A.M. ; the dif- 

 ference being more than one-third of the minimum rate. 



Sleep came on in two of the series of continuous observations, and 

 the time of its occurrence was also that of the lowest quantities of 

 air inspired. 



The amount of breathing was greater in the standing than in the 

 sitting posture, and greater sitting than lying. It was increased by 

 riding on horseback, according to the pace, also by riding in or upon 

 an omnibus. In railway travelling the increase was greater in a 

 second- than in a first-class carriage, and greatest in the third-class 

 and on the engine. An increase was also produced by rowing, 

 swimming, walking, running, carrying weights, ascending and de- 

 scending steps, and the labour of the tread- wheel ; and in several of 

 these cases the rate of increase was determined for different degrees 

 of exertion used. Reading aloud and singing, and the movement 

 recommended by Dr. Hall for restoring suspended respiration, in- 

 creased the quantity ; bending forwards whilst sitting, lessened it. 



The quantity of inspired air was increased by exposure to the 

 heat and light of the sun, and lessened in darkness. Increase and 

 decrease of artificial heat produced corresponding effects ; and the 



