XXVII. Experiments on respiration.—Second communication. On the action of foods upon the respiration during the primary processes of digestion

• Published in: Philosophical Transactions of the Royal Society of London
• Format: Article in Journal/Newspaper
• Language: English
• Published: The Royal Society 1859
• Subjects: General Medicine; Carbonic acid
• Online Access: http://dx.doi.org/10.1098/rstl.1859.0027; https://royalsocietypublishing.org/doi/pdf/10.1098/rstl.1859.0027

In 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 phenomena during the day, due to the temporary influence of food, and that the maximum influence of food always occurs in from 1½ to 2½ 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 minimum 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 materially 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; but since, as has been just mentioned, so great a part of the latter would have occurred if the food had been withheld, it is impossible to affirm that it was due to its influence. This has afforded me an inquiry of a well-defined nature, and one which my apparatus permitted me to make with ease; and it is one, moreover, so far as I know, not heretofore pursued.