EFFECTS OF EXERCISE AND SLEEP. 225 



whilst by fasting it is diminished : and, according to 

 Eegnault and Reiset, it is greater when animals are fed 

 on farinaceous food than when fed on meat. Spirituous 

 drinks, especially when taken on an empty stomach, ,are 

 generally believed to produce an immediate and marked 

 diminution in the quantity of this gas exhaled. Recent 

 observations by Dr. Edward Smith, however, furnish some 

 singular results on this subject. Dr. Smith found, for 

 example, that the effects produced by spirituous drinks 

 depend much on the kind of drink taken. Pure alcohol 

 tended rather to increase than to lessen respiratory changes, 

 and the amount, therefore, of carbonic acid expired : rum, 

 ale and porter, also sherry, had very similar effects. On 

 the other hand, brandy, whisky and gin, particularly the 

 latter, almost always lessened the respiratory changes, and 

 consequently the amount of carbonic acid exhaled. 



i. Exercise and Sleep. Bodily exercise, in moderation, 

 increases the quantity to about one-third more than it is 

 during rest: and for about an hour after exercise, the 

 volume of the air expired in the minute is increased about 

 1 1 8 cubic inches : and the quantity of carbonic acid about 

 7- 8 cubic inches per minute. Violent exercise, such as 

 full labour on the treadwheel, still further increases, 

 according to Dr. E. Smith, the amount of the acid exhaled. 

 During sleep, on the other hand, there is a considerable 

 diminution in the quantity of this gas evolved ; a result 

 probably in great measure dependent on the tranquillity of 

 breathing : directly after walking, there is a great, though 

 quickly transitory, increase in the amount exhaled. A 

 larger quantity is exhaled when the barometer is low than 

 when it is high. 



3. The Oxygen in respired air is always less than in the 

 same air before respiration, and its diminution is generally 

 proportionate to the increase of the carbonic acid. The 

 experiments of Valentin and Brunner seem to show, that, 

 for every volume of carbonic acid exhaled into the air, 



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