4 o6 THE POPULAR SCIENCE MONTHLY. 



The investigations of Liebig, who first studied this question, and 

 those of his school, demonstrate that certain salts are closely combined 

 with the other elements of living bodies, forming integral parts of 

 them. In all the tissues of the organism is found potash in combina- 

 tion usually with phosphoric acid. In the. blood the salts of soda pre- 

 dominate. When we reduce the organs to ashes, these vary but very 

 little in quality or in quantity. It is unquestionable that without these 

 salts no organ is developed, and that there is no secretion by the glan- 

 dular cellules. All the secretions contain certain salts, most of them 

 characteristic. These salts have definite functions to discharge in the 

 animal economy. Still, we do not know the quantity of these salts 

 which must enter into the food, to support the body, though this is a 

 highly-important question in the hygiene of alimentation. Direct 

 experiments alone could decide, for Voit shows that those made by 

 Magendie, and which are so frequently referred to, do not establish the 

 points they are supposed to establish. Recent studies upon the nutri- 

 tive value of gelatine have shown that Magendie failed to take into 

 account some of the principal points of the question he was considering. 



" For a long time," says Voit, " it had been my purpose to ascer- 

 tain by thorough experimentation the value of salts in nutrition, with 

 a view to examining how long an animal could live without them, and 

 what symptoms it would manifest. For this purpose I had accu- 

 mulated a quantity of the residuum of meat-extract. In the mean time 

 appeared a remarkable work by Kemmerich, in which were proposed 

 other questions, having a bearing, in many respects, upon those I had 

 proposed to myself. Kemmerich starts out with the supposition, 

 which Liebig, too, admits, that the residuum of the meat, without the 

 extract, has no value as nutriment. According to his investigations, 

 the action of meat-extract is attributable to the potash it contains, 

 whence he concludes that the residuum is of no value for nutrition, 

 owing to the absence of the potash. He therefore attempted to utilize it 

 by adding to it the salts contained in meat. To this moist residuum, 

 three times exhausted by boiling, he adds an artificial mixture of the 

 salts of meat and common table-salt; and on this food exclusively he 

 fed two dogs six weeks old, they devouring it ravenously. The ex- 

 periment was continued for three months, and at the end of that period 

 the dogs had gained considerably in weight." 



Kemmerich repeated his experiments on the same animals, giving 

 them now the residuum without the mixture of salts. He now ob- 

 served that the animals consumed less and less from day to day, even 

 when suffering from hunger. Again, experimenting on two dogs six 

 weeks old, he fed to the one the residuum mixed with the salts ; to the 

 other the residuum mixed only with common table-salt. After twenty- 

 one days a wide difference was observable between the two animals. 

 The first one weighed much more than the second, was stronger and 

 more intelligent. The second one had gained a little in weight, it ia 



