312 PROPERTIES OF THE COLLOIDAL CONSTITUENTS 



Mineral effective 

 Substance, concentration. 



HC1 m /240 



NaOH w /so 



AgNOs . - v. -' m /iso 



FeCla ...',.... .... ; "Veo 



HgCl 2 

 Aid. 



CaCl 2 



SrCl 2 



BaCh 



MgCl 2 



KC1 



NH 4 C1 



NaCl 



LiCl 



Sodium oxalate 



Sodium citrate 



to 



Vi 



The effects observed were not attributable to the imbibition of water 

 from these hypotonic solutions because, it will be recollected, the skin 

 of the frog is not permeable to water in the direction exterior -> tissues, 

 but only in the opposite direction. The only hypertonic solutions 

 employed, in which osmotic phenomena might have played a role, 

 were those of the chlorides of the alkalies and ammonium. 



It was first discovered by Biedermann in 1880 that solutions of 

 certain Sodium Salts cause skeletal muscles which may be immersed 

 in them to enter into more or less rhythmic contractions, reminiscent 

 of those of heart-muscles in normal serum or in Ringer's solution. He 

 also pointed out that since these contractions continue to take place in 

 the presence of Curare, which paralyzes the neuromuscular junctions, 

 the stimulus which evokes them must originate in the muscular tissues 

 themselves, i. e., the contractions are Myogenic. This phenomenon 

 was reinvestigated by Loeb, who found the following minimal con- 

 centrations of the various sodium salts just sufficed to evoke the semi- 

 rhythmic contractions in frogs' muscles, the solutions being rendered 

 isotonic with amphibian serum by the addition of sugar or urea. 



Minimal effective 



Substance. concentration. 



Sodium chloride . ... . ... . m /ie 



Sodium bromide . . . . ... . ;'"'.. . . . . . m /u to m /s2 



Sodium iodide . . . . .' . . . '. , . r . . m /32 



Sodium carbonate . . . . . m /ie to m /32 



Sodium sulphate . . . . . m / 32 



Sodium acetate . . . -. w / 32 to m /64 



Sodium fluoride TO / 64 to OT / 3 6 



Sodium formate m / 80 to w /ieo 



Sodium oxalate TO / 26 o to m /3oo 



Sodium phosphate . TO /i 2 8 to m /266 



Sodium citrate "/ 2 oo 



It will be observed that the most efficient stimulators in this series 

 are the salts of sodium combined with an acid (oxalic, phosphoric, 

 citric, hydrofluoric) which precipitates Calcium from its solutions. 



