280 Buchanan 



the pointer niio-ht o-iv,' a hio-h reading when Photo. 6 A was taken, the 

 artificial stimulus used when Photo. 6 B was taken only caused his 

 fingers to bend over so as to touch the dynamometer, but hardlj- to com- 

 press it at all, and not enough to make the pointer move. The electrical 

 response began about two-hundredths of a second after a short-circuit to 

 the induction shocks had been broken by the break-key inside the dark 

 box, and appears as a series of separate meniscus excursions succeeding 

 one another at regular intervals of time (corresponding to that between 

 each two breaks), not all precisely alike but each being the expression of 

 a short and strong electrical variation beginning with relative negativity 

 at the proximal contact and ending with relative negativit}* at the distal 

 contact. To begin with each contact seems to have become in turn negative 

 to the other by the same amount, but after about half a second the relative 

 negativity of the distal contact (made with the skin over the tendons of 

 the muscle) seems to have become greater than had been the relative 

 negativity of the other contact (made with the skin over the most actively 

 contracting part of the mu.scle) immediately before. The same indication 

 (greater steepness of descent than of ascent) of the relative negativity 

 becoming greater at the contact made with the skin over the tendons, 

 appears in many of the records obtained when the will supplies the stimulus, 

 but only when, as here, the distal electrode made as large a surface of 

 contact as the proximal (e.g. fig. 5 A). It must be remembered that 

 negativity of a contact with an active spot of muscle to one with a spot 

 known to be inactive is often followed by positivity to it (Journ. of 

 Physiol., xxiii., p. 335), so that when two possibly active spots are record- 

 ing, the relative negativity of the last one to become active may be the sum 

 of the negativity of its own contact and of the positivity of the proximal 

 contact. I have never noticed greater steepness of descent in the records 

 (greater velocity of the abostial than of the adostial movement of the 

 meniscus) when both contacts have been made with skin directly over the 

 muscle itself, i.e. presumably with nearly equall}' active parts of the 

 muscle. 



The steepness of each ascent and descent in the artificial tetanus record 

 presents a contrast to that observed in any of the undulations which 

 can be recognised as distinct in the record obtained when the very same 

 muscle (or group of muscles) was contracting in response to the will, and 

 producing a far greater mechanical effect. The meniscus always came to 

 rest between each two excursions ; and it did so also, although for a shorter 

 time, when the core was in the primary coil, as is shown by two records taken 

 under such conditions. When the exciting electrodes were not near enough 

 to the median nerve to provoke contraction of the muscle (i.e. movement 

 of fingers or of wrist or of both), the photographs showed that the meniscus 

 remained at its resting position throughout, even when the shocks were 

 distinctly felt down the arm as well as up it (see Addendum, p. 241). 



