20 FOOD INGESTION AND ENERGY TRANSFORMATIONS. 



oxygen consumption per minute. These varied considerably with 

 different conditions of body activity and after the ingestion of food. 

 Speck's several papers appeared between 1865 and 1892, but were 

 brought together and summarized by him in one publication. 1 In his 

 earliest communication on the influence of food ingestion 2 he observed 

 that the respiratory exchange was increased about 12 per cent by an 

 ordinary mixed diet. In another series, published by him in 1874, 3 

 he reports numerous experiments with food and concludes that the 

 respiratory exchange is increased after the noon meal 25 per cent. This 

 marked increase in heat production, which takes place, he finds, within 

 30 minutes after a meal, led him to the belief that the work of digestion 

 must cause this increased gaseous metabolism, since it is not to be 

 expected that much food would be absorbed into the blood within the 

 short space of 30 minutes. From the protein experiments 4 he concludes 

 that 2 hours after the meal the height of digestion is passed and that 

 at the end of 4 hours digestion is completed. In the sugar experiments 

 he finds that 1 hour after the ingestion of sugar the digestion ceases. 

 In two experiments with coffee he records a small but visible rise in the 

 metabolism. Two experiments were made likewise on the effect of 

 water-drinking and of flooding the body with water for some time before 

 the experiment. According to his results, when the water is taken the 

 evening before and to within an hour of the experiment in the morning 

 there is no influence upon the metabolism; when the water is taken a 

 short time before the experiment, that is, 1,250 c.c. in an hour, and the 

 experiment is made about 30 minutes after the completion of the water- 

 drinking, he notes a marked rise in the gaseous metabolism. 



Fredericq, 1882. By using a most ingenious apparatus, called by 

 him an "oxygenographe," Fredericq, 5 in the laboratory at Liege, was 

 able to determine the oxygen consumption directly on man both before 

 and after taking food. This apparatus is a modification of an earlier 

 form devised for animals. It is of special interest in that the oxygen 

 is supplied to the apparatus by means of a movable bell floating in a 

 bath of chloride of calcium solution, a principle which underlies the 

 present universal respiration apparatus so extensively used in this and 

 other laboratories. The carbon dioxide is absorbed by a mixture of 

 lime and caustic soda, but the oxygen consumption is the only factor 

 measured. Fredericq concludes that digestion is accompanied by a 

 marked increase in the consumption of oxygen and illustrates this by 

 several interesting curves of oxygen consumption throughout the day 

 which show the relationship of this factor to the time in which food was 



'Speck, Physiologic dea menschlichen Athmens, 1892. 



2 Speck, Tagebl. d. 46 Vers. d. Naturf. u. Aerate in Wiesbaden, 1873, p. 136. 



3 Speck, Arch. f. exp. Path. u. Pharm., 1X74, 2, p. 405. 



4 Speck, Physiologic des menschlichen Athmens. 1892. 



'Fredericq, Arch, de Biol., 1882, 3, p. 687; Elements de Physiologic Humaine, 2d ed., 1888. 



