716 PHYSIOLOGY OF RESPIRATION. 



In starvation, when the body is living only on its own protein and 

 fat, the R. Q. is lower than under a normal diet, falling from about 

 0.8 to 0.7, and a similar drop is observed in diabetes, since in this con- 

 dition also the body is burning only protein and fats. By a deter- 

 mination of the respiratory quotient before and after varying certain 

 conditions one may ascertain whether the given condition causes 

 a change in the character of the body metabolism. For example, 

 Higgins finds that alcohol given to an individual may cause a fall 

 in the R. Q. in a few minutes. Since alcohol when burnt has a low 

 coefficient, 0.667, this result is interpreted to mean that the alcohol 

 is being burnt promptly in the body. In nutritional experiments 

 the R. Q. is used very commonly as an index of the proportions of 

 fat and carbohydrate that are being consumed in the body. Under 

 certain exceptional conditions the R. Q. may rise even above unity. 

 In convalescence, for instance, after a wasting disease when the 

 individual is increasing rapidly in weight from the formation of new 

 body fat, or in certain animals, geese, in which fat may be made to 

 form readily by excessive feeding of carbohydrates. In such cases 

 an oxygen-rich food 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. 



Modified Respiratory Movements. Laughing, coughing, yawn- 

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

 as modified respiratory movements, since the same group of muscles 

 comes into play. These are all movements, with the exception of 

 yawning, which may be regarded as reflexes that have nothing to 

 do directly with the processes of respiration. A most interesting 

 variation of the normal type of respiration is known as the Cheyne- 

 Stokes respiration. It occurs in certain pathological conditions, 

 such as arteriosclerosis, uremic states, fatty degeneration of the 

 heart, and especially under conditions of increased intracranial 

 pressure. It is characterized by the fact that the respiratory 

 movements occur in groups (10 to 30) separated by apneic pauses, 

 which may last for a number (30 to 40) of seconds. After each pause 

 the respirations begin with a small movement, gradually increase 

 to a maximum, and then fall off gradually to the point of complete 

 cessation (see Fig. 282) . Great variations, however, are shown in 

 the character and number of the respirations during the so-called 

 dyspneic phase. From observations made by means of the 

 sphygmomanometer Eyster* has shown that in this condition 

 there are also rhythmic waves of blood-pressure (Traube-Hering 

 waves), and according to the relation of these pressure waves to 

 the groups of respirations the Cheyne-Stokes cases fall into two 

 groups. In one group the dyspneic phase coincides with a fall 



* Eyster, Journal of Experimental Medicine," 1906. 



