In the first instance, careful search should be made for any sign of injury, especially on the head. The discovery of a severe scalp wound or of a fracture of the skull, in association with the symptoms of concussion or compression, will in most cases raise the presumption that the unconsciousness is due to some traumatic intra-cranial lesion. Examination of the fluid withdrawn by lumbar puncture may furnish useful information (p. 338). In the absence of evidence of a head injury, the stomach should be washed out and its contents examined to see if any narcotic poison is present. The urine also should be drawn off and examined for albumin and sugar. In hæmorrhage due to the rupture of diseased cerebral arteries (apoplexy), or to embolism, the symptoms are essentially those of compression, and, in the absence of a definite history of injury to the head, it is seldom possible to arrive at an accurate diagnosis as to the cause of the condition. The history that the patient has previously had "an apoplectic shock," and the fact that he is up in years and shows signs of arterial degeneration and of cardiac hypertrophy which would favour such hæmorrhage, are presumptive evidence that the lesion is not traumatic. If a history is forthcoming that the patient is an epileptic, there is a strong presumption that the symptoms are those of _epileptic coma_. In _alcoholic poisoning_ the examination of the stomach contents will furnish evidence. The patient is not completely unconscious, nor is he paralysed; the pupils are usually contracted, but react; and the temperature is often markedly subnormal. Improvement soon takes place after the stomach has been emptied. In _opium poisoning_ the general condition of the patient is much the same as in poisoning by alcohol. The pupils, however, are markedly contracted, and do not react to light. When the poison has been taken in the form of laudanum, this may be recognised by its odour. In the _coma_ of _uræmia_ or of _diabetes_ there is no true paralysis, nor is there stertor. The urine contains albumin or sugar, and there may be œdema of the feet and legs. _Prognosis._--The prognosis depends so much on the nature and extent of the injury to the brain that it is impossible to formulate any general statements with regard to it. It may be said, however, that the symptoms which indicate a bad prognosis are immediate rise of temperature, particularly if it goes above 104° F., the early onset of muscular rigidity, extreme and persistent contraction of the pupils, with loss of the reflex to light, conjugate deviation of the eyes, and the early appearance of bed-sores. In the majority of cases compression ends fatally in from two to seven days. On the other hand, recovery may ensue after the stuporous condition has lasted for several weeks.