78 DYNAMICS OF LIVING MATTER 



2. CONCERNING A THEORY OF IRRITABILITY AND THE ROLE OF NA, 



K, AND CA FOR ANIMAL LIFE 



In 1899 I outlined a general theory of irritability which may be 

 briefly summarized in the following sentences which I quote from a 

 former paper: "The salts, or electrolytes in general, do not exist in 

 living tissues as such exclusively, but are partly in combination with 

 proteids (or fatty acids). The salts or electrolytes do not enter into this 

 combination as a whole, but through their ions. The great importance 

 of these ion-proteid compounds (or soaps) lies in the fact that, by the 

 substitution of one ion for another, the physical properties of the 

 proteid compounds change (e.g. their surface tension, their power to 

 absorb water, or their viscosity or state of matter). We thus possess 

 in these ion-proteid or soap compounds essential constituents of living 

 matter, which can be modified at desire, and hence enable us to vary 

 and control the life phenomena themselves." * 



Life phenomena, and especially irritability, depend "on the pres- 

 ence in the tissues of a number of various metal proteids, or soaps (Na, 

 Ca, K, and Mg), in definite proportions." 



I first applied this conception to a phenomenon which had hitherto 

 been observed only occasionally ; namely, rhythmical contraction of the 

 muscles of the skeleton.f I found that such rhythmical contractions 

 occur only in solutions of electrolytes, i.e. in compounds which are 

 capable of ionization. In solutions of nonconductors (urea, various 

 sugars, and glycerine), these rhythmical contractions are entirely or 

 practically impossible. Only in certain, not in all, salt solutions are 

 such rhythmical contractions possible. All the solutions of Na-salts 

 are able to produce them, but in a 0.7 per cent NaCl solution, contrac- 

 tions begin later, and are less powerful, than in an equimolccular 

 NaBr solution. The experiments on the rhythmical contractions of the 

 muscles of the skeleton led to some other data concerning the effects 

 of those salts. Solutions of Na-salts produce rhythmical contractions 

 only if the muscle cells contain Ca-ions in sufficient numbers. As soon 

 as there is a lack of Ca-ions in the tissues, the Na-ions are no longer 

 able to cause rhythmical contractions. On the other hand, if we add 

 Ca-salts in sufficient quantity to the NaCl solution, it will no longer 

 cause rhythmical contraction in a fresh muscle of the frog. It there- 



* Loeb, Am. Jour. Physiology, Vol. 3, p. 337, 1900. 



t Loeb, Festschrift fur Professor Pick, Wiirzburg, 1899. 



The idea of the general existence of such ion-proteid compounds was developed inde- 

 pendently by Pauli and myself in 1899. Loeb, Pfliigei j s Archiv, Vol. 75, p. 303, 1899 ; and 

 Festschrift fur Pick, 1899 ; and W. Pauli, Wiener akaJemischer Anzeiger, October 12, 1899 ; 

 and Ueber physikalisch-chemische Methoden und Probletne in der Medizin, Wien, 1900. 



