ION-PROTEID COMPOUNDS 545 



weight of water in an equimolecular KC1 solution. In an 

 equimolecular CaCl 2 solution it lost about 20 per cent, of 

 water. In a LiCl solution it neither lost nor absorbed any 

 water. The same was true for the bromides and iodides of 

 the same metals. Even organic compounds of these metals 

 showed somewhat the same difference, although the effects 

 of the anion in these cases modified the results quantita- 

 tively. This difference between the effects of the various 

 metal ions upon the absorption of water by the muscle 

 shows a remarkable parallelism with the influence of the 

 same ions upon the absorption of water in soaps. There are 

 Na, K, Ca and other soaps. While K soaps absorb enor- 

 mous quantities of water the Na soaps absorb much less 

 and the Ca soaps still less than the Na soaps. If in the Na 

 soap we substitute K ions for the Na ions, the soap takes up 

 quantities of water. If we substitute Ca ions for Na ions, 

 the soap loses water. From this I concluded that in the 

 muscle the various metal ions exist in combinations in which 

 they can as easily be substituted for each other as in the 

 soap compounds. These compounds are similar to the soap 

 compounds in one physical quality, namely, the absorption 

 of water. I expressed the opinion that the ions in muscle 

 must be in combination with proteids. If a muscle be put 

 into a KC1 solution, the K ions of the solution enter the 

 muscle and gradually take the place of the Na and Ca ions 

 in these metal proteids. The K proteids are able to bind 

 more water than the Na or Ca proteids. If the muscle be 

 put into a solution of CaCl a , Ca ions will take the place of 

 the Na and K ions in the proteid compounds of the muscle, 

 and the muscle must lose water. I have carried these ex- 

 periments farther and may publish some of the more recent 

 results in this series of articles. 



I next applied this conception of ion-proteid compounds 

 to a phenomenon which had hitherto been observed only 



