ELECTROLYTES IN LIVING MATTER 85 



I at first believed that I was dealing here only with a break shock 

 caused by the muscle's own current; but this was contradicted by 

 various facts: first, that only those individual fibers contracted which 

 were lifted out of the solution, while the others remained relaxed; 

 second, that the latent period for the contraction after the muscle 

 has left the solution is too long; namely, as much as a second 

 or more. The most convincing proofs against such an assumption 

 are, however, the following facts. The irritability of the muscle for 

 the contact reaction does not reach its maximum at once, but only 

 after a certain time. When the sensitiveness of the muscle has reached 

 its height, a glycerine or a sugar solution can be substituted for 

 the citrate solution. Whenever the muscle is at that time taken out 

 from the glycerine or sugar solution and brought into contact with 

 the air, the contraction occurs; while it ceases when the muscle is put 

 back into the sugar solution. After a short time, however, the muscle 

 loses its contact irritability in the sugar or glycerine solution. These 

 experiments, however, certainly prove that the contact reaction is not a 

 break shock caused by the resting current of the muscle itself when it 

 is lifted out of the citrate solution. 



It is a very interesting and theoretically important fact that the 

 muscle loses this peculiar form of irritability very soon when it remains 

 in contact with air, oil, sugar solution, glycerine, or salt solutions, 

 different from those that produce this specific irritability. In LiCl or 

 NaCl solutions the contact irritability is lost as fast, if not faster, than 

 in a sugar or glycerine solution. We can reestablish the irritability, 

 however, by putting the muscle back into the sodium citrate solution 

 for some time. This fact, together with those mentioned before, suggests 

 the following as the most probable explanation of the peculiar phenomena 

 of contraction with which we are dealing in this case. The solutions 

 which produce the contact irritability possess anions which are liable 

 to form insoluble calcium compounds. Whatever the effects of these 

 anions may be, the fact that in less than a minute the contact effects are 

 noticeable, indicates that only the surface layer of the muscle, or the 

 surface layer of each individual fiber, is altered. It is impossible for 

 the anions to migrate deeper into the muscle in so short a time. In 

 the surface layer of the muscle or the individual fibers, we have there- 

 fore temporarily a diminution of Ca-ions. We have then a muscle 

 whose surface layer differs from that of an ordinary excised muscle. 

 If this layer is once established, the muscle contracts at any change from 

 the citrate, carbonate, fluoride, etc., solutions to air, CO 2 , oil, 2 n sugar 

 solution, glycerine, chloroform, or toluol. If the muscle be left in these 

 media, or put into a NaCl or a CaCl 2 solution, it loses this contact 



