After a certain number of months, or, according to Duchene, a year has elapsed, changes can be noticed in the muscles, and the weakness becomes more marked. The calves of the legs become enlarged, so as to give the appearance of unusual vigour, and generally a similar hypertrophy affects other muscles as well. The gluteal muscles, the muscles of the thighs, the posterior muscles of the spine, the deltoids, and sometimes almost all the muscles of the trunk and limbs may share in this enlargement. If the muscles do not become hypertrophied, they usually waste, and this diminution in size of some muscles renders more striking the extraordi nary hypertrophy which affects other muscles in their neighbourhood.
As the weakness of the muscles goes on progressively increasing, the characteristic attitude and gait become more and more marked. At the same time any slight extra strain put upon the muscles in the performance of certain acts increases the difficulty to such a degree that the child is re duced to some very curious expedients in order to accomplish them suc cessfully. Thus, in rising from a chair, he endeavours to assist the extension of the knee-joint by placing a hand on each femur just above the knee. By this means, especially if at the same time he bend forwards, he transfers a large part of the weight from the extremity (the hip) of a lever whose fulcrum is at the knee to a part of the lever close to the fulcrum ; or, even, if the body is bent forwards sufficiently to throw the centre of gravity in front of the knees, actually uses the weight to be moved as a motor power to effect the straightening of the knee-joint. Again, in extending the hip-joints the patient begins by placing his hands, as iu the former case, just above the knee, and then moves the hands alternately higher and higher until the straight position is arrived at.
For some time the muscles retain sufficient power to carry the patient at a moderate pace along a level surface ; but he cannot jump, and in mounting the stairs he is forced to do so on his hands and knees. If told to get up from the ground, the child can only obey by going through a series of elaborate manoeuvres, all calculated to relieve or assist the weakened muscles. As Dr. Gowers describes the process, the patient, being on all fours, keeps his hands on the ground, and stretches the legs out behind him far apart. Then, still keeping the body supported chiefly
by the hands, he manages by shuffling backwards on the toes to get the knees extended. The body is thus supported by the hands and feet all placed as widely apart as possible. Next, the hands are alternately moved backwards along the ground so as to bring the larger portion of the weight of the trunk over the legs. Then, one hand is placed on the knee, and a push with this, and with the other still on the ground, is sufficient to enable the extensors of the hip to bring the trunk into the upright po sition. In many cases the child cannot rise at all unless near to some piece of furniture, by means of which he can gradually hoist his trunk up wards with his hands. • As the paralysis extends the patient gets more and more helpless; and when the upper limbs become affected, as usually happens after a few years have elapsed, his condition is very distressing.
The affected muscles do not always increase in size. Sometimes they waste, and the hypertrophy and atrophy are irregularly distributed. Usu ally many more muscles are wasted than are enlarged. The hypertro phy is apt to affect by preference certain muscles. The muscles of the calf, the vasti of the thigh, the glutaei, the infra spinati, and the del toids are often enlarged. On the contrary, the muscles on the front of the leg are more usually wasted, and wasting is also more common in the latissimus dorsi and the sterno-costal portion of the great pectoral muscle. In the arm the biceps and triceps may be enlarged, but the muscles of the forearm are rarely affected. Sometimes the temporals and masseters are hypertrophied. In some rare cases the muscles, before they begin to enlarge, have been noticed to be smaller than natural.
This form of paralysis is not accompanied by any general fever, but Dr. Ord has noticed a higher temperature in the leg where the muscles are hypertrophied than in the corresponding thigh. This, however, is not a constant phenomenon. At first the muscles respond normally, or nearly so, to the galvanic current, both interrupted and continuous ; but when greatly wasted, the muscular response is weak, or even absent. The knee reflex is usually notably diminished. Sensation, however, is unimpaired, and there is perfect control over the bladder and sphincter.