EFFECTS OF FOOD ON THE CARBONIC ACID. 845 



mum product occurs in spring (April and May), and the minimum at 

 the end of summer (September), a gradual increase occurring in early 

 winter (October, November, and December), and a gradual decrease 

 in early summer (June, July and August). Hence, heat, as the re- 

 sult of seasonal changes, equally with artificial heat, diminishes the 

 quantity of carbonic acid exhaled, and climatic cold increases it ; 

 moreover, it was found by Barral, that the daily quantity of carbon 

 exhaled by the skin and lungs, was, in winter, upwards of 5000 grains, 

 and in summer only about 8700 grains. But neither temperature 

 alone, nor this, added to the effects of atmospheric pressure, account 

 for the seasonal changes. (E. Smith.) It may be remarked, however, 

 that the hygrometric condition of the air in the above researches, was 

 not taken into account, but this, as shown by Lehmann, is of the 

 highest importance ; the period of increase corresponded with the wet 

 months, and that of decrease with the dry months of the year. 



Food generally increases the absolute quantity of carbonic acid 

 given off from the lungs, whilst fasting has the opposite effect, the pro- 

 portion of carbonic acid in a given quantity of the expired air being, 

 however, greater during starvation. Thus, in a person six feet high, 

 in whom the average quantity of carbon exhaled, when at rest, with 

 ordinary diet, was 7.85 oz., the daily quantity exhaled whilst fasting, 

 was 5.9 oz. ; the diminution produced by fasting for the 24 hours, 

 being rather more than one fourth the usual quantity exhaled when 

 taking food. (E. Smith.) The quantity exhaled in fasting, sinks to a 

 certain line, which has been named the basal line, below which, in 

 health, it does not descend, but prolonged starvation ultimately di- 

 minishes it. The influence of food has been shown, by an increase after 

 breakfast of one-fourth the previous quantity, and after dinner of 

 about two-thirds (Scharling) ; the chief increase noted by Dr. Smith, 

 was after breakfast and tea, and not after early dinner. Thus, the 

 average quantity of carbonic acid exhaled, by a certain person, being 

 20.6 cubic inches (9.77 grs.) per minute, the quantity during continu- 

 ous fasting being about 14 cubic inches (6.61 grs.), and the maximum 

 and minimum quantities in the working day with food, 22 cubic inches 

 (10.43 grs.) and 14.2 cubic inches (6.74 grs.), the increased exhalation 

 after breakfast and tea was from 4.2 to 6.3 cubic inches (from 2 to 3 

 grains), and after early dinner only from 2.1 to 4.2 cubic inches (from 

 1 to 2 grains). The different effect of different kinds of food and 

 drink, as observed by Dr. Smith, is, in some respects, remarkable : all 

 nitrogenous foods increase the exhalation of carbonic acid ; and so 

 does any mixture of nitrogenous matters with the carbhydrates, such 

 as is found in bread, oatmeal, and milk ; but pure starch has scarcely 

 any effect; pure fat seems even to diminish the quantity of carbonic 

 acid evolved, though pure sugar increases it. Tea, coffee, and cocoa 

 cause an increase more sudden and marked than that produced by any 

 other substances experimented with ; pure alcohol also increases the 

 quantity; but of the spirits ordinarily in use, rum increases the quan- 

 tity, brandy and gin diminish it, whilst whiskey varies in its effects ; 

 wine and ale increase it, whilst the volatile or aromatic ingredients of 

 both spirits and wine, seem to lessen the quantity exhaled. Distilled 



