ELECTROLYTES IN LIVING MATTER 91 







coagulation of milk, where this enzyme seems solely concerned in ren- 

 dering available Ca, which naturally is held in organic combination in 

 the milk in such a form as to be of no use for the process of coagulation.* 



A word may be said in regard to the difference in the behavior of the 

 isolated center of Gonionemus and Polyorchis toward a pure solution 

 of NaCl. The former begins to beat in such a solution almost instantly, 

 the other as a rule only after a long interval. The difference may con- 

 sist simply in the fact that the cells of Gonionemus have from the start 

 enough Ca in an available form, while this is not the case in Polyorchis. 

 In the case of the former, the beats can begin immediately in a pure 

 NaCl solution, while in the latter this is not possible. 



The question may now be asked, What keeps the normal heart 

 beat or the normal contractions of the jellyfish going? I believe the 

 conditions are the same as those discussed in muscles, the strips of ven- 

 tricle, or the center of the Medusa, with this difference only, that the 

 salts or ions, which according to our hypothesis are needed for that 

 purpose, are all supplied from within. I am inclined to believe that 

 the constant chemical changes, such as oxidations, or the production 

 of CO 2 , or other processes, lead also to an effect which in the isolated 

 center can be brought about by certain salts, such as citrates or oxalates ; 

 namely, the setting free of Ca so that it may form dissociable colloidal 

 compounds and be then either replaced by Na or K, or vice versa. It 

 is possible that the CO 2 formed in the muscle may aid in this process. 



The margin of a jellyfish which contains the central nervous system 

 contracts for a time at least, rhythmically in any solution, and certainly 

 in solutions of NaCl, KC1, and CaCl 2 . I was surprised to find that the 

 addition of MgCl 2 to any of these solutions makes the contractions of 

 the margin more normal, as I believe, in an indirect way. For successful 

 rhythmical contractions it is necessary that a real relaxation follows the 

 contraction. I noticed that the edge of a Polyorchis has a tendency to 

 remain permanently contracted in a mixture of 100 NaCl, 2 KC1, 2 CaCl a , 

 and this tendency finally interfered with the contractions. This effect 

 is due to the Ca. I found, however, that upon the addition of MgCl 2 

 this tendency to a continued contraction lessened and the Medusa 

 showed a more normal type of contractions. 



If it be true that the process of stimulation consists in an exchange 

 of Na- and K-ions for Ca-ions (or Mg-ions?), or vice versa, in the tissues, 

 and that normal irritability depends upon the presence of these ions 

 in definite proportion in the tissues, it is to be expected that a change 

 in these proportions would alter the irritability and give the tissues 

 properties which they do not possess normally. I have already mentioned 



* Loevenhart, loc. cit. 



