562 



obtained from actual observation ; and hence much valuable labour has 

 been lost and science has been led into erroneous channels. I have 

 therefore ventured to lay before the Royal Society, with a view to pub- 

 lication in its ' Proceedings,' a short summary of the conditions which 

 I believe to be essential to the elimination of truthful results in in- 

 quiries connected with the rate of pulsation and respiration, the quan- 

 tity of air inspired, of carbonic acid expired, and of urinary water and 

 urea excreted, the weight of the body, and the influence of foods ; and 

 in so doing I purpose first to consider the inquiries into the daily quan- 

 tities of each of them, and then to refer to each subject separately. 



1. The determination of the daily quantities. 



In none of the subjects for inquiry will observations made at one or 

 a few periods of the day enable us to infer the total daily quantities, 

 since there are scarcely any two hours in which the quantities remain 

 unchanged ; and although the variations, for the most part, follow a 

 definite course, the progression is not so uniform that, even under 

 the most favourable circumstances, they may be safely inferred. 



The rate of pulsation and respiration varies in such a manner that 

 it is increased after 'each meal during about two hours, and then de- 

 clines for about an equal period, unless food be in the meantime taken. 

 There is a less proportionate increase and decrease after the early 

 dinner and tea than, after breakfast, and at about 8 or 9 P.M. the rate 

 falls rapidly and continually until the middle hours of the night. The 

 nearest approach to a stationary rate occurs 1st, in the middle hours 

 of the night, with a tendency to increase ; 2nd, after rising and before 

 breakfast, with a tendency to decrease ; and 3rd, in the afternoon, 

 when the midday meal has been deferred, with a tendency to increase 

 at the usual meal-hour. The least stationary periods are the three or 

 four hours following each meal, and the late hours in the evening. In 

 the total absence of food throughout a whole day, the rate remains 

 nearly stationary from the hour of rising in the morning until about 9 

 P.M., with a tendency to change at the usual meal-hours. 



The quantity of air inspired and of carbonic acid expired is subject 

 to similar variations ; but the increase after the early dinner is less* 

 and that after tea is greater than that of the rate of pulsation, and the 

 rate is more constant before breakfast and throughout a day of fasting. 



The rate of evolution of urea is less uniform than that of either of 



