632 PHYSIOLOGY OF RESPIRATION. 



In the same way it may be estimated that the R. Q. for the oxidation 

 of proteids alone is equal to 0.78. 



In accordance with these conclusions it is found practically 

 that the respiratory quotient may be raised to 1, approximately at 

 least, by feeding exclusively upon carbohydrate foods, while an 

 excess of proteid or carbohydrate food lowers it to 0.7. In con- 

 nection with other data, therefore, the R. Q. may be used to 

 throw light upon the character of the nutrition. Under certain 

 special conditions the respiratory quotient may exceed unity or 

 fall distinctly below 0.7. A rise to a value over unity may occur 

 temporarily because of increased ventilation of the alveoli. Deeper 

 and more rapid breathing will drive out some of the C0 2 in the air 

 of the lungs and thus increase greatly the R. Q. As previously 

 stated, this increase has in itself no nutritional significance, but it is 



Fig. 252. Record showing typical Cheyne-Stokes respiration (from a case of aortic and 

 mitral insufficiency with arteriosclerosis). The time record gives seconds. 



a factor that must be allowed for in such experiments. A more 

 suggestive increase of the R. Q. is observed during convalescence. 

 In this period, as is well known, an individual may increase in 

 weight rapidly, chiefly from the laying on of fat. This fat is made 

 in large part probably from the carbohydrate of the food. An 

 oxygen-rich food, therefore, is converted to an oxygen poor one, 

 so that some of the oxygen must be split off partly as carbon 

 dioxid, and there is a larger output of this substance in the expired 

 air. Under many conditions of life muscular exercise, for example 

 in which the oxidations of the body are greatly increased, the 

 larger production of C0 2 is balanced by a larger absorption of O. 

 It is interesting to find that usually this balance is so well maintained 

 that the R. Q. does not vary sensibly. 



Modified Respiratory Movements. Laughing, coughing, 

 yawning, sneezing, sobbing, and even vomiting may be considered 



