57 Ziemssen's Cyclopædia, Amer. ed., vol. xi. p. 409.
Hitzig58 states that in certain pathological conditions where the ganglionic elements (in the cord) are superexcitable, the least disturbance produced on one side, and which determines there a voluntary movement, may be communicated to the other side, and provoke, according to the case, either movements similar to a voluntary one or a spasmodic movement which is really a contraction; and also in certain cases relations of the same nature may be established among cellular groups quite distant from each other; and we can comprehend that in these cases the voluntary movements executed by the sound side may be re-echoed in that which is diseased.
58 Quoted by Charcot, loc. cit., p. 124.
This apparent digression bears an important relation to the pathology of copodyscinesia, and lends force to the view that the associated movements which occur in the well arm, or in the affected arm when the sound side is used, or even in the face and legs, and which are quite often seen in these affections, are due to the fact that there is a central change.
Mitchell,59 in speaking of functional spasms, states that it will be found in all these cases that when an ordinary functional motor act gives rise to spasms elsewhere, these occur in muscles which have physiological, and therefore anatomical, relations to the muscles which by their normal use give rise to the morbid activities. He considers that there is a hypersensitizing of the sensory centre which takes record of the activities of the affected muscles.
59 “Functional Spasms,” Amer. J. Med. Sciences, Oct., 1876.
The fact that the left hand becomes implicated in some cases where it is used to relieve the right should be mentioned in this connection as lending weight to this hypothesis, especially as in a few cases of telegraphers' cramp the left hand has been found implicated in the very first attempt to use it in telegraphing.
Poore60 considers this transfer as no evidence that the change is central, and is one of the few who consider the pathological conditions as purely peripheral in character. Hamilton61 and De Watteville62 also consider the peripheral hypothesis the correct one.
60 Loc. cit.
61 Nervous Diseases, Philada., 1881.