In marked contrast with this profound trophic disturbance of the bones is the intact nutrition of the skin. The absence of decubitus is indeed an important diagnostic mark from ordinary myelitis. The subcutaneous fat, however, wastes so completely that the skin seems to be closely adherent to the subjacent tissues, and cannot be pinched up into folds.
The temperature of the skin always falls; the limb is perceptibly colder to the touch than its fellow, and is often bluish and cyanotic. Heine has observed that the temperature diminishes gradually from the centre to the periphery, and at the coldest point may sink to 14° R.54 Hammond relates a case where the local temperature was 75° in an atmosphere of 72°. The author says that exact measurements of surface temperature should be taken with Lombard's differential calorimeter, especially when convalescence is expected, as then a rise of temperature, however slight, is of most favorable augury.
54 Loc. cit., p. 16. This is not a difference of 14 degrees between the sound and paralyzed limbs, as is erroneously quoted by Seeligmüller (loc. cit., p. 67).
General factors contribute to the fall of temperature: diminished blood-supply from shrinkage of blood-vessels, or even atrophy of a certain number among these; loss of nerve-influence upon the oxidation processes; loss of muscular contractions, which should attract an afflux of blood. Among these factors the loss of nerve-supply is probably the most important, since the others exist in cerebral paralysis without causing the remarkable coldness characteristic of anterior poliomyelitis.
The atrophy of the blood-vessels is not always confined to the terminal twigs. The entire iliac artery, and even the lower part of the aorta, have been found markedly diminished in calibre.55 This shrinkage is unaccompanied by any change in the walls of the blood-vessels: it is a simple arrest of development. It strikingly illustrates the dependence of the blood-vessels on the vascular demands of the tissues they are destined to supply.
55 Charcot and Joffroy, Archives de Phys., 1870, case by Séguin, loc. cit., p. 9.
The changes which take place in the electrical reactions of the paralyzed limbs rank in importance with their paralysis and their atrophy. They serve to establish the diagnosis, to decide, to a large extent, the prognosis, and to measure the degree of nervo-muscular degeneration.
It is well known that the early diminution, and even entire loss, of faradic contractility was first emphasized by Duchenne as pathognomonic of infantile spinal paralysis. Contractility is diminished in from three to five days after the occurrence of the paralysis, and by the end of a week is completely lost in those muscles in which the paralysis is to be permanent. The muscles which recover spontaneously during the period of early regression recover their faradic with their voluntary contractility. In others, persistently but less profoundly paralyzed and susceptible of cure, the faradic contractility remains simply diminished and in unequal degrees. Progress to recovery under treatment is usually marked by progressive increase in the faradic response; but sometimes the power of voluntary contraction is fully regained, while the faradic response is still permanently lessened. The loss of faradic contractility is more complete and permanent in muscles irretrievably paralyzed by anterior poliomyelitis than in any other disease. These laws have been generally accepted by late observers.56
56 Simon disputes their validity, and declares that the importance of electricity in the diagnosis of spinal paralysis may easily be exaggerated (Union médicale, 7, 28, p. 942, 1879).
In 1868, Salomon discovered that muscles in which faradic contractility had been completely lost were nevertheless capable of contracting under the stimulus of galvanism—that this contraction is exaggerated, and sometimes occurs at the opening as well as at the closing of the circuit.57 The author remarks that the persistence of galvanic reaction after the complete loss of faradic contractility is completely analogous to an observation of Brucke's on muscles poisoned by woorara,58 where the intramuscular termination of the nerve is paralyzed. It is to be inferred, therefore, in both cases that the muscular contraction results from direct irritation of the muscle, and implies the entire loss of influence from the nerve.