348 Prof. J. S. Macdonald. [Apr. 17, 
through such an organ would take place towards the nerved end of the 
organ, and, in the surrounding conductors, a current would pass in the 
reverse direction, that is to say, away from the nerved end of the organ. 
The colloid solution to make an organ of this new kind might conveniently 
be taken either from nervous tissue itself, in which the electrolyte is of this 
character, or it might be taken from epithelial masses elsewhere, since we 
may conclude, from the constant “ingoing ” direction of the current detected 
in such masses, that here, also, the negative kation is that possessing the 
more rapid motion. It is not surprising, therefore, to find that the observa- 
tions made upon the electrical organ of Malapterurus have served to destroy 
the all-sufficiency of Pacini’s rule. 
It is obvious, also, that once the admissibility of the conceptions thus used 
to explain the main facts of nerve and muscle function, and the function of 
the electrical organs of fishes has gained acceptance, the same conception can 
also be at once advanced in explanation of a large number of the phenomena 
exhibited by every excitable tissue. Inhibition and excitation in the central 
nervous system, in the heart and vascular tissues; the condition of tone ; 
the flow of water through secretory surfaces; in fact, all conditions reacting 
to nerve discharges with comparative rapidity. They are also applicable to 
the case of unnerved tissues, such, for example, as the instance of the 
ciliated epithelium mentioned previously. An examination of the “blaze 
currents,” elicited from so many tissues by Waller, might conceivably reveal 
many instances which might find their explanation in the use of these 
conceptions. 
In general the conception might be stated briefly thus. A unit in a state 
of inhibition is one in which the state of colloid solution is more perfect than 
normal. In this condition the inorganic salts, and therefore the electrolytes, 
are mostly bereft of all the influence they possess in virtue of the number and 
motion of their molecules. A unit in a state of excitation 1s one, on the other 
hand, in which these molecules are in a state of motion, a condition produced 
by the degradation of the colloid solution of the unit. A unit in a state of 
tone is in a condition intermediate between these states. Again, character- 
istic differences between the functions of different units may in some cases 
find their explanation in the comparative freedom allowed to the released 
molecules, and also to physical differences between the molecules released, 
such as differences in electrical charge and rate of motion. 
Returning for a moment to the special case of nerve, it might be pointed 
out that the hypothesis would lead one to expect the possibility of finding 
nerve-fibres capable of communicating a positive charge, in place of the more 
usual negative charge, to the tissues innervated by them. This might 
