422 OF NUTRITION. 



body has already been given ( 68), and it has been shown that the ordinary 

 diet of the working man contains between 250 and 300 grains of nitrogen, 

 and between 4000 and 5000 grains of carbon ; that he consumes besides 

 about five pints of water and a very variable quantity (200-600 grains) of 

 salts ; lastly, that he requires about 11,000 grains of oxygen. These collec- 

 tively constitute the Ingesta. The Egesta are represented by the excretions 

 of the Kidneys, Bowels, Lungs, and Skin, 1 which are composed of the more 

 or less completely oxidized constituents of the food and tissues, as well as 

 in the case of the alvine evacuations of the indigestible residue of the food. 

 If the weight of the body remain stationary, the Egesta must necessarily be 

 precisely equal to the Ingesta. But if the quantity of food consumed be 

 greater than necessary, then one of several events may occur : either it fails 

 to be absorbed, and is simply discharged by the bowels, as in an experiment 

 of Kauke, who found that with 64 oz. of meat 22^ oz. were thus eliminated 

 unaltered ; or (as in the case of water and salts) it may be absorbed, and be 

 immediately discharged by the kidneys and skin ; or it may be absorbed 

 and be deposited in the body (as often occurs with fat), increasing its weight; 

 or lastly, it may minister to the performance of more work, and after under- 

 going oxidation may increase the Egesta generally. If again the supplies 

 of food be insufficient in quantity the weight of the body must diminish, the 

 excreta remaining the same, or the weight of the body being maintained the 

 excreta must diminish. Speaking generally, the increased demand for food 

 and the increase of the Egesta are associated with increased activity of the 

 cell functions throughout the body, which may express themselves in the 

 formation of more abundant secretions, the more rapid circulation of the 

 blood, and the greater energy of the nervo-muscular apparatus. Bidder 

 and Schmidt estimate that the respective amounts of the various digestive 

 fluids which are daily poured into the alimentary canal of an adult Man 

 weighing 14 stone, are nearly as follows : 



Oz. Grains. 



Saliva, 56.8 containing 233 of solid matter. 



Bile, 56.8 " 1208 " 



Gastric juice, .... 147.2 " 2976 " 



Pancreatic fluid, ... 7.1 " 310 " 



Intestinal juice, ... 7.1 " 46 " 



So that nearly 10 oz. (troy) of solid matter are separated from the blood in 

 the digestive secretions, for the purpose of introducing new alimentary ma- 

 terials of not more than two or three times the amount ; and thus we see 

 that a large portion of the food ingested and assimilated must be consumed 

 in providing for the introduction of a further supply, in addition to that 

 which, when duly assimilated, is applied by the nutritive processes to the 

 repair of the solid tissues. All these processes imply the more active absorp- 

 tion of oxygen and a corresponding increase in the excreta, which are essen- 

 tially products of combustion, so that when the muscles are powerfully ex- 

 erted a larger amount of carbonic acid and water is excreted, whilst if the 

 activity of the glands is increased more urea (containing the chief portion 

 of the nitrogen of the ingesta) is eliminated. It must be understood, how- 

 ever, that it is not owing to the quantity of oxygen absorbed that the general 

 activity of the cells throughout the body is augmented, but the activity of 

 these regulates the amount of oxygen absorbed. This is well shown by the 

 fact that whilst, as Ewald has pointed out, the oxygeuatiou of the Hiemo- 



1 To which may be added the fluids discharged at stated periods by the Mammary 

 Glands, Testes, and Uterus. 



