328 PHYSIOLOGICAL CHEMISTRY 



the formation of acid hematin respectively. Hemoglobin may be 

 more accurately determined using one of the ordinary forms of colori- 

 meter and either the carbon monoxide hemoglobin method of Palmer 1 

 or the acid hematin method as applied by Cohen and Smith 2 and 

 Robscheit. 3 In each of these methods, the standard is controlled by 

 the Van Slyke gasometric method (see above). 



9. Determination of Respiratory Exchange. The output of carbon 

 dioxide and consumption of oxygen by the human body during a given 

 period of time may be measured by means of one of a number of rela- 

 tively simple forms of respiration apparatus which have been developed 

 of recent years. 4 These have found their chief clinical application 

 in the study of patients with suspected thyroid disease, hyperthyroidism 

 bringing about an increase and hypothyroidism a decrease in the basal 

 metabolic rate or the minimal heat production of the body at complete 

 muscular rest 12 to 18 hours after the ingestion of food. The direct 

 measurement of this heat production involves the use of a complicated 

 respiration calorimeter, but it is easily measured indirectly from the 

 oxygen consumption and with a fair degree of accuracy. An idea as 

 to the increased consumption of oxygen during muscular work may also 

 be obtained by collecting the air expired by the working individual 

 in a large air-tight bag carried over the shoulders, measuring and analyz- 

 ing it for oxygen and carbon dioxide. 5 



10. Simple Demonstration of the Presence of Carbon Dioxide in Expired 

 Air. (a) Into each of two small flasks or large test tubes introduce 25 c.c. of a 

 clear saturated solution of barium hydroxide. After an ordinary inspiration, 

 expire through a bent glass tube or pipette dipped beneath the surface of the 

 solution in the first flask. Repeat the experiment with flask number two but 

 hold the breath as long as possible after the inspiration before breathing out 

 through the tube. Note the relative amounts of precipitate of barium carbonate' 

 formed. 



(b) Into each of two large test tubes introduce about 20 c.c. of water and 

 1-2 drops of saturated barium hydroxide solution. To the first add a few drops 

 of phenolphthalein solution and to the second a few drops of phenolsulphone- 

 phthalein solution. Expire through each of these until a change takes place. 

 What does this change indicate? 



Calmer, W. W.: Jour. Biol. Chem., 33, 119, 1918. 



2 Cohen, B., and Smith, N A. H.: Jour. Biol. Chem., 39, 489, 1919. 



3 Robscheit, P\ S.: Jour. Biol. Chem., 41, 209, 1920. 



4 Benedict, F. G.: Boston Med. and Surg. Jour., 178, 567, 1918. Boothby, W. M., and 

 Sandiford, I.: "Basal Metabolic Rate Determinations," W. B. Saunders, Philadelphia, 

 1920. Jones, H. M.: Jour. Am. Med. Ass'n., 75, 538, 1920. 



6 R. G. Peafce in Macleod, J. J. R. : "Physiology and Biochemistry in Modern Medicine," 

 p. 554, C. V. Mosby Co., St. Louis, 1918. 



