88 STUDIES IN ELECTRO-PHYSIOLOGY: 



moist tissues and only partial insulation by the skin. This 

 no doubt gives us the average reading on the galvanometer 

 scale of ordinary normal deflections, except in the case of 

 the finger-tips and toes, which give constant readings and 

 are probably the earth (air) outlets of the nervous system. 



" At the finger-tips, no matter how dry the skin may 

 be, we are always able to measure a current. Also reversal 

 of sign is obtained from hand to hand and from the thumb 

 to the fingers of the same hand. 



" With other portions of the skin over the body a com- 

 paratively dry condition will lead to no current being 

 obtained, while moisture will produce a current equal in 

 E.M.F. at any part. 



" In testing the body as apart from the hand-to-hand 

 measurement, Mr. Baines uses a larger electrode to a fixed 

 point and goes over the body with one of smaller diameter. 

 By this means the sign, which is unimportant, remains the 

 same, and it becomes easier to estimate the deflections due 

 to faulty condition. It has been claimed that these 

 currents are ' skin currents ' and that a metal electrode 

 of larger size, with moist skin, will set up a current, and 

 that the use of electrodes of similar size will lead to different 

 readings, change of sign, etc. I have elsewhere shown that 

 skin and metal to skin and metal through the galvanometer 

 does not always exhibit current, so we must look further 

 for an explanation. 



" If we note the different thicknesses of the skin, apart 

 from pressure areas, we find that where the greatest depth 

 of connective tissue is, or where there is greatest vascularity, 

 the skin is, as a rule, thicker ; and that even in specially 

 vascular areas, like the scalp, there is a special arrangement 

 of skin and connective tissue, we are able to trace in it some 

 purpose. If, then, we remember the fact that the develop- 

 ing foetus is open, and that later it is joined down the 

 centre line, and that fibrous tissue is a non-conductor, we 



