vii.] AN OBITER FACTUM 127 



and perpendicular to it. The electrodes are connected with 

 the house current, which is at 1 10 volts. Out of caution for my 

 own comfort, I have means of taking any desired fraction of the 

 whole current ; and to tell what current I am taking, there is a 

 milliamperemeter in circuit with my arm. The electrodes have 

 are?e of about seven square centimetres, and a current of between 

 two and three milliamperes should produce a distinct result in 

 about five minutes.. The kathode is, I believe, nearer to the 

 wrist, the anode above it ; but we shall soon see, for it is at the 

 kathode that we shall find evidence of penetration of the coloured 

 anion, MnO 4 . 



The trial is over ; and after washing the forearm under the 

 tap, you see a number of indelible brown spots over the pre- 

 viously kathodic area of the skin, which are due to its penetra- 

 tion by the coloured anion, which you remember travels against 

 the current, and therefore gets into the body where the current 

 leaves it. Notice their clearly defined punctiform appearance ; 

 this signifies that the path of current has been chiefly, if not 

 entirely, by way of the sweat-ducts, hardly or not at all through 

 the general epidermic investment. 



A similar principle of transport holds good in the case 

 of other electrolytes, and it is interesting to note, in the 

 case of poisonous salts, whether it is the anode or the 

 kathode that acts as the channel of introduction. In most 

 cases, e.g., in that of strychnine sulphate, the poisonous 

 property belongs to the base, the kation, which penetrates at 

 the anode ; in others, e.g., in that of cyanide of potassium, it 

 belongs to the acidic moiety, the anion, which penetrates by the 

 kathode. In the first case the anode is the poison carrier, the 

 kathode being innocuous ; in the second case it is the kathode 

 that kills. If, following the example of Leduc, I should place 

 two rabbits side by side, connecting them by a couple of elec- 

 trodes of indifferent nature, i.e., soaked in NaCl, and then 

 run a current through both rabbits in series, by means of elec- 

 trodes moistened with strychnine sulphate, I should put the 

 anodic rabbit into strychnine convulsions by reason of pene- 

 tration of the kation, while the kathodic rabbit, taking in only 

 the non-toxic anion, would remain quite unaffected. 



