190 Prof. A. B. Macallum and Miss M. L. Menten. [July 24, 



brought into suspension (or " solution ") in chloride-free water the chloride 

 only slowly diffuse into the fluid surrounding or enveloping each particle. 

 To account fully for such a result one may suppose that the chlorides, so 

 difficult to remove, are in the fluid which obtains in the interior of the 

 particles, the superficial layer of each of which is permeable (or impermeable) 

 to such a degree as its extreme tenuity would permit.* 



Suspensions of such chloride-holding molecular aggregates in waterf would 

 manifest some degree of electrical conductivity, for if the suspended particles 

 were numerous enough to form a more or less continuous series, the 

 ionisation necessary for conductivity would occur, but the velocity of the 

 ions, at least of those remaining in the interior of the particles, would be 

 diminished. All this has a bearing on the question of nerve conductivity and 

 on the nature of the nerve impulse itself. 



The nerve axon consists in large part of colloids (proteids) in suspension, 

 and in such a degree of concentration as to give a firm consistency to the 

 axon.^ In the particles of this suspension a part at least of the chloride or 



* The same explanation may be advanced in the case of some inorganic colloids. In 

 colloidal silica subjected to prolonged dialysis sodium compounds are present (Jordis and 

 Kanter, 'Zeit. fur anorg. Chemie,' vol. 34, p. 455, vol. 35, p. 16). In the case of colloidal 

 ferric hydroxide " solution," Hantzsch (' Annalen der Chemie,' vol. 323, p. 1) found that 

 silver nitrate did not precipitate all the chlorine present, and that the ferric hydroxide 

 precipitate, obtained by the addition of salts, although very carefully 'washed, still 

 contained chlorine, whose presence, however, could only be demonstrated after the washed 

 precipitate was fused with soda. Spiro (' Beitrage zur Chem. Physiol, und Path.,' vol. 5, 

 p. 276) found colloidal ferric hydroxide "solutions" even after months of dialysis to 

 contain ionised as well as non-ionised chlorine, and, from quantitative analyses of the 

 dialysed solutions, came to the conclusion that free hydrochloric acid is not present, and 

 that colloidal ferric hydroxide is not a simple compound, but a substance of complicated 

 constitution, or, much more probably, a mixture of compounds. 



Is it not more reasonable to suppose that the peripheral layers of each colloid particle 

 exercise a restraining influence on the transfer of the ions ? That colloid material can 

 manifest greatly diminished permeability to the ions, can be seen in an exaggerated 

 degree in the case of the red blood corpuscle (ox and cat), in the cell-contents of which 

 are electrolytes, but owing to impermeability of its membrane to ions it is a non-conductor 

 (Bugarszky and Tangl, 'Centralbl. fiir Physiol.,' vol. 11, p. 297). And yet when such a 

 corpuscle is placed in a hypotonic solution it yields to the latter not only its electrolytes, 

 but also its haemoglobin ! 



t It may be that the so-associated quantity of chlorides and, perhaps, of other 

 inorganic compounds, equally difficult to remove, constitute the factor responsible for the 

 very slight osmotic pressure and the very slight depression of the freezing point shown 

 by presumably pure proteids. 



% The haemoglobin in the mammalian red corpuscle is 26 to 30 per cent., and the 

 proteids of muscle approximate 20 per cent., but probably amount to more in the 

 individual fibres. About 20 per cent, of solids would appear to be necessary to give the 

 firm character to the axon which it possesses. It may be that the colloids and the water 

 in the axon in their relations of solubility may occur in the two-phase system. 



