After a period, varying from a few minutes to several hours, he rallies, the first evidence often being vomiting, which is usually repeated. Sometimes reaction is ushered in by a mild epileptiform seizure. He then turns on his side, the face becomes flushed, and gradually the symptoms pass off and consciousness returns. The temperature rises to 99° or 100° F., and in some cases remains elevated for a few days. In most cases it falls again to 97° or 97.5°, and remains persistently subnormal for one or two weeks. During reaction the pulse becomes quick and bounding, but after a few hours it again becomes slow, and usually remains abnormally slow (40 to 60) for ten or fourteen days. There is sometimes a tendency to constipation, and for the bladder to become distended, although he has no difficulty in passing water. Very commonly the patient complains of pain in the head for some days after the return of consciousness. Children often sleep a great deal during the first few days, but sometimes they are very fretful. In cases complicated by gross brain lesions the symptoms of concussion may imperceptibly merge into those of compression or there may be a "lucid interval" of some hours duration. _After-Effects of Concussion._--The majority of patients recover completely. A number complain for a time of headache, languor, muscular weakness, and incapacity for sustained effort--_traumatic neurasthenia_. Sometimes there is a condition of mental instability, the patient is easily excited, and is unduly affected by alcohol or other stimulants. Occasionally there is permanent mental impairment. It is not uncommon to find that the patient has entirely forgotten the circumstances of the injury and of the events which immediately preceded it. In some instances the memory is permanently impaired. On the other hand, it has occurred that a patient, after concussion, has recovered his memory of a foreign language long since forgotten. As it is never possible to determine the precise extent of the damage to the brain, the immediate prognosis, even in the mildest cases of concussion, should always be guarded. If the patient has been actually unconscious, the condition should be looked upon as a serious one, and treated accordingly.