such cases the heart is primarily at fault, and the condition is termed syncope. Although in practice it is most important to distinguish syncope from more strictly cerebral coma, yet it must be admitted (and such admission is important for therapeutics) that in both categories of cases anæmia of the brain (cerebral cortex) is the essential factor or immediate cause of suspension of consciousness. This view of the pathology of coma is borne out by the fact that the condition may be produced at will, experimentally or therapeutically, by compression of both carotid arteries. It may be well to mention here the pseudo-coma of hysteria. In these cases consciousness is really present, as shown by responses to violent cutaneous irritations (faradic brush), by quivering of the closed eyelids and resistance to attempts to open them, by vascular or muscular movements evoked by remarks of a flattering or abusive nature made in the patient's hearing, and by cessation of the condition after complete closure of the nose and mouth for forty-five seconds or one minute (asphyxia). In the typically unconscious state, as in cases of fracture of the skull or of intracranial pressure by exudations, clots, tumors, etc., there are several objective symptoms to be noted. The pupils are usually dilated and immovable (exceptions chiefly in narcotic poisoning); the pulse is reduced in frequency and retarded; it is sometimes full and bounding, or in other cases feeble and irregular. The breathing is often slow and irregular; the patient fills out his cheeks and puffs (smokes the pipe); sometimes the Cheyne-Stokes type of respiration is observed. In hysterical or hypnotic impairment of consciousness these important symptoms are absent: the patient seems simply asleep. Although coma is, strictly speaking, a {27} symptom, it so often appears as the leading one of a group that it deserves study almost as a disease. Indeed, there are few more difficult problems for the physician than the case of a comatose subject without a good history of the preceding condition, causes, etc. It is impossible here to consider all the possibilities of this problem in diagnosis;[1] we can only state the chief and most probable pathological conditions which may cause coma. [Footnote 1: An able attempt at the differential diagnosis of comatose cases, by J. Hughlings-Jackson, will be found in _Reynolds's System of Medicine_, Am. ed., 1879, vol. i. p. 920.] (1) The patient may be epileptic. The following signs of a past convulsive attack should be sought for: a bitten tongue, fleabite-like ecchymoses on the face, neck, and chest, saliva about the face and neck, evidences of micturition or of seminal emission in the clothing, etc. There is usually a small rise of temperature after a single fit, and consciousness soon returns without assistance, or a second seizure appears.