1813.] emitted from the Lungs during Respiration. 3.S5 



Illustrations of Law II. — The circumstances which imme- 

 diately increase the quantity of carbonic acid appear to be com- 

 paratively few, while those which decrease it are very numerous. 

 The effects of the former class, also, are very inconsiderable and 

 transient ; while those of the latter, on the contrary, are much 

 greater and more permanent. 



The following are the chief circumstances which I have 

 noticed to act in one or other of these ways ; and, in conformity 

 to the law, it will be found, by recurring to the list of experi- 

 ments at the end of this part of the essay, that their action 

 having ceased the standard was sooner or later resumed. 



Exercise. — The effects of this are very various, according to 

 its nature and degree, and according also to the time of its dura- 

 tion. Moderate exercise, as walking, seems always at first to 

 increase its quantity; but after having been continued for a cer- 

 tain time, it ceases to produce this e fleet ; and if prolonged so 

 as to induce fatigue, the quantity is diminished. On the con- 

 trary, violent exercise seems to lessen its quantity even from the 

 first ; 01 if it does increase it, the effects are very trifling and 

 evanescent. After violent exercise the quantity is always very 

 much lessened. To this head also may perhaps be referred the 

 act of speaking. I have found after a long silence the effects of 

 speaking to be, to produce a slight increase, which, however, 

 was only momentary, though the speaking was still continued. 

 The exhilarating passions, also, to which perhaps the above 

 might be referred in some degree, seem to produce a similar 

 effect. Sec Exper. 1, 2, 3, 4, and 5. 



Food.— No doubt different kinds of food have very different 

 effects. As my object, however, at present, has been chiefly to 

 discover general laws, I have not paid so much attention to this 

 part of the subject as it demands, and which 1 intend to do. 

 During the period in which these experiments were making, as 

 before observed, 1 kept myself as regular as possible, with respect 

 to food, &c, and only partook of the most simple, in order that 

 it might not interfere with their results. The effects observed 

 from food, therefore, have not been remarkable, and apparently 

 little more than to keep up the quantity to the standard, and 

 sometimes to raise it a little above, certainly never to depress it 

 below, unless 1 took some fermented liquor, and then it was 

 always depressed, as will be seen immediately. Long abstinence 

 and fatigue certainly lessen the quantity; the former, however, 

 wheR not in the extreme, hardly so much as might be expected. 

 'I hua I have found the quantity very little depressed, after fasting 

 £1 hour., below the usual standard, and what it probably would 

 have been had I taken my breakfast as usual. See Exper. 6 and 

 7. Alcohol, and all liquors containing it, which ! have tried, 

 have been found to have the remarkable property of diminishing 



