42 The theory of course assumes the truth of the demonstration by which atrophic paralysis is rendered symptomatic of disease of the spinal cord, and the nutrition of a muscle dependent on the integrity of the muscles of origin of its nerves.
In the arm two mutually correlative cases are observed: (a) Immunity of the supinator longus during paralysis of the forearm muscles; (b) paralysis of the supinator in association with paralysis of the deltoid, biceps, and brachialis anticus. The latter constitutes Remak's upper-arm type of localization, and is exhibited in his first case.43
43 Loc. cit.; also, cases 1st and 2d by Ferrier, in which, however, other shoulder-muscles were involved.
Ferrier has experimentally confirmed this muscular association by means of isolated irritation of the fourth cervical nerve, which threw into contraction the supinator longus, together with the deltoid, biceps, and brachialis internus. At the same time, in the experiment the flexors and extensors of the wrist were excited, while in the special form of paralysis noted they were exempt. This electrical method is a less precise mode of analysis than the pathological, for the double reason that (a) fibres whose nuclei are dissociated may pass together in the same root; (b) because the same muscles receive fibres from more than one root: thus the flexors and extensors of the wrist from the fifth as well as the fourth cervical. Thus when the nucleus of the latter was destroyed paralysis would be averted by means of the fibres coming from the fifth root.
The experiment and the pathological observation, however, concur in indicating that the fibres innervating the supinator longus, though passing to it in the path afforded by the radial nerve, afterward ascend in the cord to a ganglionic nucleus in close proximity to those of the upper-arm muscles specified—liable, therefore, to be affected with them. The purpose effected by such association is the supination of the arm.
It is excitation of the fourth root in Ferrier's experiment which gives results most closely corresponding to Remak's observations. Excitations of the fifth and sixth root reveal other combinations, which Ferrier has found realized in adult's spinal paralysis. Thus in his second case, in addition to the group of muscles already mentioned, the rhomboid, infraspinatus, and serratus magnus were paralyzed, the last muscle indicating complication with the fifth root. In the third and fourth cases muscles supplied from the sixth root were joined to those innervated by the fourth and fifth—namely, the pectoralis major and latissimus dorsi.
In this upper-arm type the muscles affected are supplied by three different nerve-stems—the axillary, musculo-cutaneous, and the radial. In the forearm type the most common variety consists in paralysis of the extensors of the wrist, thus exactly imitating lead palsy.44 The supinator remains intact, the intrinsic muscles of the hand are sometimes intact, sometimes paralyzed. Sometimes, however, the extensors are relatively intact; the interossei are atrophied, and a clawed hand, resembling that characteristic of cervical hypertrophic pachymeningitis, is developed.45
44 It is on this fact, indeed, that Remak has been led to argue the spinal nature of saturnine paralysis (“Zur Pathogenie der Blei lahmung,” Archiv für Psych., Bd. vi., 1876).
45 The march of this disease, together with that of tabes dorsalis, furnishes data for localizing the nervous nucleus for the wrist extensors. In both diseases the lesion is ascending: in tabes disturbance of sensibility occurs first in the distribution of the sensory fibres of the ulnar nerve; in cervical pachymeningitis the flexors and intrinsic muscles of the hand are first paralyzed. Hence it is to be inferred that the central nucleus for the latter muscles lies in the lower, that for the extensor muscles in the middle, segment of the cervical enlargement of the cord.
The much greater frequency of extensor paralysis in the forearm type of anterior poliomyelitis indicates that the lesion of this disease begins about the middle of the cervical enlargement (see note).