In the upper extremities rigid contractions are much less frequent, even in proportion to the number of paralyses. Seeligmüller has seen five cases of reducible flexion of the fingers, and one of permanent extension of the wrist and fingers, associated with paralysis of all the flexors. In this case, if the arms were so suspended that the hand hung freely, its weight gradually overcame the action of the extensors and the fingers fell into flexion. Upon any attempt at exertion the hyperextension was reproduced.
DEFORMITIES OF THE TRUNK.—Scoliosis will be caused when, with unilateral paralysis of the extensors of the vertical column, the lower part of the trunk is drawn to the non-paralyzed side, and the upper half is bent over the paralyzed side in order to restore the balance. In bilateral paralysis of the extensors both shoulders are projected backward, so that a plumb-line dropped from between them falls behind the sacrum, and lordosis is developed, although the lumbar column is not projected forward. The same form of lordosis occurs when the glutæi are paralyzed. When, however, the abdominal muscles are paralyzed, the lumbar column is really projected forward, and then a plumb-line dropped from the shoulders passes over the sacrum.69
69 Duchenne, loc. cit., 1861.
PARALYSIS OF THE ABDOMINAL MUSCLES.—Unilateral paralysis of the extensors of the back is often difficult to detect in young children. Seeligmüller recommends that the child be laid across the mother's knees and told to move the trunk from one side to the other while the pelvis is held firm. If too young to obey the direction, the movement can be excited by pricking or by electric irritation. It will be seen that the trunk can be turned only to one side.
In these paralyses of the trunk it is clear that the deformity does not develop under the influence of muscular antagonism alone, but only when the non-paralyzed muscles attempt to sustain the superincumbent weight of the body or a portion of it.
SUMMARY OF MECHANISMS OF THE DEFORMITIES.—We may indeed conclude, as stated at the beginning, that this complex etiology exists in almost all cases. When the limb is at rest in bed or the weight of the body is transferred to crutches, then repeated contraction of the flexus will suffice to bring the limb into a vicious position (contraction at knee- and hip-joint). When the foot or hand hangs unsupported, its weight is sufficient to cause deformity, even when all the muscles are paralyzed, and sometimes in opposition to the direction of intact muscles. Thus the weight which is passively borne by the limb, and the efforts of intact muscles to effect the function of the limb in spite of the paralysis, both concur in the production of the deformity.
ANATOMICAL LESIONS.—The theory of the anatomical basis of infantile paralysis constitutes one of the most interesting portions of its history. It is indeed one of the most instructive chapters of modern pathology from the rapidity with which in a short time precise knowledge has accumulated, and for the degree in which this has revolutionized previous ideas.
Autopsies.—Until 1863 only five autopsies had been made upon persons affected with infantile paralysis.70 As the disease was never, of itself, fatal, opportunity for pathological investigation did not present itself, while attention was still vividly attracted to the paralysis. When this had become a chronic infirmity, and patients had succumbed to intercurrent disease, the opportunity must have occurred, but was not then utilized.
70 I believe the first list of modern autopsies was made by myself in a paper read before the New York County Medical Society, Dec. 22, 1873. The paper was not published until May, 1874, and in the mean time Seguin's lecture on “Infantile Paralysis” was published in the N. Y. Med. Record, Jan. 15, 1874, with a tabulated list of 25 autopsies, necessarily almost identical with mv own—cases 9 and 10 are really identical. A case by Roth is included; 4 negative autopsies are omitted. In 1880, Seeligmüller, in his elaborate essay in Gerhardt's Handbuch, published a list of 32 cases, including the above, and adding to them the following: Case by Müller, 1871; 4 cases by Leyden, 1875 (Arch. de Psych.); 1 case by Raymond, 1874 (Gaz. méd. de Paris); 1 case by Demme, 1876 (B. med. Bericht über das Jennerischt Kinderspital zu Bern); 1 case by Eisenlohr, 1876 (Tageblatt des Hamburger Naturforscher Versammlung); 1 case by Schultze, 1877 (Virch. Arch., Bd. lviii.).
To this list we may now add 3 cases by Turner, Humphrey, Taylor, 1881 (Path. Trans. London); 2 cases by Dejerine, 1878 (Progrès méd.), giving a total of 37 cases with detailed histories and autopsies.