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XXVII. Experiments on Bespimtion.-—-%QQ,oYA Communication. On the Action of Foods 
upon the Bespiration during the primary processes of digestion. By Edwaed Smith, 
M.B., LL.B. {Bond.), M.B.C.P., Corresponding Member of the Academie des Sciences 
et Lettres de Montpellier, and of the Natural History Society of Montreal, Assistant- 
Physician to the Hospital for Consumption, Brompton, &c. Communicated by Sir B. 
C. Beodie, Bart, P.B.S. 
Eeceived January 6,— Bead February 10, 1859. 
ty a paper which I have recently had the honour to forward to the Royal Society, I 
showed that there are alternate elevations and depressions of all the respiratory pheno- 
mena durmg the day, due to the temporary influence of food, and that the maximum 
influence of food always occurs in from li to 2| hours after the meal. I also proved, 
from the state of the system in a prolonged fast, as well as from the tolerably uniform 
state at the end of the interval between the meals, that there is on each day a basal or 
normal line below which the amount of respiratory action does not ordinarily fall ; and 
I also showed that there is a maximum elevation from food which is tolerably uniform, 
and which is the most pronounced after the breakfast and tea meals. Hence it appeared 
that the influence of food is in two degrees:— 1st, that which lies between those two lines 
and exceeds the normal or basal line; and 2nd, that which sustains the system up to 
the mmimum or basal line. The former action is temporary and of short duration, 
whilst the latter is permanent. 
Proceeding from these facts, I have prosecuted a lengthened inquiry into the influence 
of numerous articles of food over the respiration, when taken separately and not in the 
combined form in which we take them at meals, and have endeavoured to ascertain 
what is their maximum effect. As nearly all food tends to sustain and increase the 
vital actions, and as in the total absence of food for a lengthened period the respiratory 
changes are sustained to the extent of 75 per cent, of that with food, my inquiries 
have been almost entirely directed to determine that influence, which acts so as to 
appear between the maximum and minimum lines just mentioned. Except within very 
narrow limits, I have not found any substance taken as food or with food which mate- 
nally lowers that minimum line; and, moreover, I do not know any method whereby 
It would be possible, in a state of health, to show the action of any substance which 
acts much below it. Hence my aim has been to show to what extent various substances 
raise the respiratory changes above or depress them below a basal line, and not merely 
to state what absolute amount of carbonic acid, for example, was evolved during their 
action. The former could be referred to no other cause than the food under experiment ; 
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