DIGESTIVE SYSTEM. 



have no proof that these substances are derived from any 

 other source than the food. Hence, for the supply of this 

 single secreted fluid, substances containing, at least, these 

 eight elementary bodies, must be obtained for the use of 

 the system. It would be difficult to determine which of 

 these substances could be spared, so as to produce the least 

 injurious alteration in the secretion ; but it is obvious, that > 

 as they all occur constantly, they are all necessary to the per- 

 fection of the secretion and the healthy state of the system. 

 As animal matter contains a great deal of azote, physio- 

 logists have differed in their opinion with respect to its ori- 

 gin, some attributing its source to the air in respiration, 

 others to. the food. M. F. MAGENDIE instituted a series 

 of experiments, for the purpose of determining this ques- 

 tion. He selected a dog in good condition, three years old, 

 and fed him with substances which contained no azote. 

 These consisted exclusively of white sugar and distilled 

 water. During the first week he appeared to enjoy his 

 new regimen, but in the second week he began to grow 

 lean, his eyes became ulcerated, and gradually losing 

 strength, he died on the thirty-second day. The urine was 

 found to be alkaline, and to present no trace of uric or 

 phosphoric acid. The bile resembled that of herbivorous 

 animals, and the excrements contained but a small propor- 

 tion of azote. In the body the fat had disappeared, the 

 muscles were reduced in size, and the volume of the intes- 

 tines diminished. Similar results were obtained, when the. 

 experiment was repeated upon two other dogs ; and like- 

 wise in two cases when olive oil, and in others, when gum 

 was substituted in place of sugar *. 



* Precis Elementaire de Physiologic, Paris 1817, 2 vols. 8vo. ii. 

 p. 390, 394. 



