The chief disorders resulting from infantile paralysis have been considered in this paper. The principal and most crippling symptoms are muscle paralysis and paresis. This is the result of lesions of the anterior-horn cells. In the affected muscles, neuromuscular degeneration can be accurately determined by chronaxia. The degree and the extent of the injury are evaluated by this test; this aids in the diagnosis and the prognosis. Inflammation of the sensory protoneurons is not necessarily found at exactly the same level as the injuries to the anterior-horn cells. Therefore, pain and tenderness of muscles are found in non-paralyzed as well as in affected muscles. Pain might be explained as a referred pain which is usually increased by the stretching of the muscles.

The Kenny concept is fundamentally different. Three cardinal symptoms are described,—muscle "spasm", "mental alienation", and "incoordination". To test this concept, a series of investigations have been carried out, since obviously a clear understanding of the symptoms is of great importance for the diagnosis, the prognosis, and the treatment of any disease. The various parts of the concept have been considered.

1. "Spasm" is not "the most damaging symptom of the disease"; it is a complex and ill-defined phenomenon, under which several different conditions are included. "Spasm" does not lead to neuromuscular degeneration.

2. In paralytic and paretic muscles called "alienated", our observations showed that there was always some degree of neuromuscular degeneration. Among these muscles, some were partially denervated; these have a good chance to recover. Some others were totally denervated, and, therefore, will not recover.

3. There is no clinical evidence of "incoordination" in the ordinary sense. The patient attempts voluntarily or involuntarily to use a stronger muscle for a weak or paralyzed one. This abnormal use of an extremity is substitution and not "incoordination".