846 SPECIAL PHYSIOLOGY. 



water has been found to diminish the exhalation of carbonic acid. 

 The opposite effects of different alcoholic fluids, such e. g. as rum and 

 brandy, are referred by Dr. Smith to the separate action of the alco- 

 hol, sugar, aromatic substances, and nitrogenous bodies in each of 

 those .fluids respectively ; and the different effects of weak alcoholic 

 liquors, and of pure alcohol, have been explained by supposing, that 

 in the former case, the alcohol may act chiefly by stimulating the re- 

 spiratory changes ; whilst in the latter, it may interfere with the oxida- 

 tion of the ordinary constituents of the body. Habitual drinkers 

 usually accumulate fat. 



From the preceding facts it would appear that the constituents of 

 food do not act in proportion to the quantity of carbon they contain ; 

 but that some specifically excite the respiratory interchanges, appa- 

 rently by increasing the processes of oxidation in the body, and by 

 augmenting the depth of the respirations, or the quantity of air in- 

 spired. Two substances, identical in composition, sugar and starch, 

 act differently ; the former exciting respiratory interchange, the latter 

 not doing so. Milk, especially when new, is a more powerful excitant 

 even than a purely albuminoid substance. The nitrogenous foods in- 

 crease the quantity from 1 to 2.1 cubic inches (from J to 1 gr.), mixed 

 nitrogenous and hydrocarbonaceous foods give an increase of about 

 4.2 cubic inches (2 grs.) per minute ; milk, a perfect mixed diet, 4 cu- 

 bic inches (nearly 2 grs.) per minute; spirits of wine 2.1 cubic inches 

 (1 gr.); rum 3 cubic inches (about 1J gr.) ; ale and stout 2.1 cubic 

 inches (1 gr.); whilst tea, coffee, and cocoa increase the evolution of 

 carbonic acid from 3 to 6.3 cubic inches (1J to 3 grs.) per minute. (E. 

 Smith.) Certain substances, such as sugar, alcoholic fluids, tea, and 

 coffee, produce their effect very quickly, reaching their maximum 

 within half an hour ; whilst flesh, bread, oatmeal, and milk act later, 

 their influence enduring as long as two hours and a half. (E. Smith.) 

 Lastly, the effect of a high diet on one day, may affect the respiratory 

 changes, as well as the excretion of urea, on the following day, im- 

 parting, as it were, a somewhat durable stimulus to the system. 



The amount of carbonic acid exhaled is diminished in all chronic 

 and organic diseases of the lungs, in hectic conditions, and in cholera ; 

 whilst it is increased in chlorosis, in which the number of the red cor- 

 puscles is diminished. The proportion of carbonic acid in a given 

 amount of expired air is increased in certain exanthematous diseases, 

 as in measles, and especially in small-pox, in which it is nearly doubled; 

 whilst, on the other hand, it is reduced about one-half in typhus fever. 

 The absolute quantities exhaled in these and other diseases, have not 

 been sufficiently investigated. 



The effects of remedial agents, generally, on the absorption of oxy- 

 gen and exhalation of carbonic acid, have likewise yet to be scientifi- 

 cally determined. The inhalation of the vapor of chloroform and 

 ether diminishes remarkably the escape of carbonic acid from the 

 blood ; and this constitutes an accessory cause affecting the nervous 

 system. In the treatment of diseases by change of climate, the in- 

 creased respiratory interchange which is induced by cold, and the di- 

 minished oxidation which takes place in higher temperatures, should 



