700 
DE. E. SMITH OH THE CHE^nClE 
however, show that observations taken at the period of the day when the quantity of 
carbonic acid evolved is at the lowest point, viz. four to five hours after a meal, will be 
nearly uniform, and that the excess due to food may be approximately arrived at by 
taking observations at to 2^ hours after the meal, and deducing the average Horn 
those quantities. , n i 
2. Without food. 
The variations in the respiratory phenomena in the working day were so small, that at 
2, 4, 6, 6, 7, 9 and 10 o’clock p.m., on July 6, all the quantities were almost identical 
with those at 7 on the following morning. The maximum and minunum quantities oi 
carbonic acid were 6-52 gi-s. and 7-44 grs. ; of aii- inspii-ed, 399 cubic inches and 341 
cubic inches ; rate of respiration 12 and 10-2, and rate of pulsation 71 and o8 per mmute 
—quantities which contrast in a remarkable manner with those preiiously shown to 
occur with food. In Plate XXXIII. fig. I, the variations with and without food are con- 
Hence there is great uniformity in the respiratory phenomena during a long fast ; but 
it was noticeable that on the occasions when the carbonic acid would have increased uith 
food, there was a slight decrease without food-=-a fact corresponding with that which I 
recorded in the Transactions of the Royal Medical and Chhmgical Society for 1856, in 
the rate of the functions on five persons of different sexes and ages. A low and uniform 
state of system is therefore the characteristic condition in a prolonged fast; and it is 
very like that which occurs with food at the end of the interval between the meals. It 
has also been shown that in a fast of this duration the quantity of carbonic acid does 
not progressively diminish, but is the same at the end of twenty-seven horn's as it was 
at the end of 4| hours. 
There is therefore a state of the system which is nearly uniform under all the cii'ciim- 
stances of the day, when the body is uninfluenced by exertion or the primary processes 
of digestion, and which may be called the basal or normal state. From this but little 
can be taken away ; and the additions must be due to exertion or the temporary influ- 
ence of compound aliments. This I shall subsequently show to be a fact of much 
interest and importance, since it will be proved that certain substances which, as food, 
must contain nutriment, do not increase the products of respiration over this basal line , 
whilst others, including all compound aliments, do produce an inciease. 
The great uniformity in the state of the system during fasting renders that period 
particularly fitted for the determination of the numerical relations between the carbonic 
acid, air inspired, and rate of pulsation and respiration, and also as a basis with uliicli 
to compare the influence of food and other agents. The law before mentioned in rMer- 
ence to myself was well exemplified in this experiment; for the cubic inches ot air 
inspired are very nearly represented by the half of the product of the pulsations and the 
respirations. There was 1 gr. of carbonic acid to 52-5 cubic niches of air; which it 
we consider it as a normal, the proportion with food is less and uuth exertion is greatei. 
