As a symptom of various diseases which affect the human organism, wakefulness is sufficiently well recognized by systematic writers on the practice of medicine, though, even here, it is very certain that its pathology has seldom been clearly made out. As a functional disorder of the brain, arising from inordinate mental activity, it has received scarcely any notice. This neglect has, doubtless, been in a great measure due to the fact that it is only within late years that the condition in question has become so common as to attract much attention. At present there are, probably, but few physicians engaged in extensive practice in any of our large cities who do not in the course of the year meet with several cases of obstinate wakefulness, unaccompanied, in the early stages at least, by any other prominent disorder of the system. In my opinion, no one cause is so productive of cerebral affections as persistent wakefulness, for not only is the brain prevented from obtaining rest, but it is kept in a state of erethism, which, if not relieved, must sooner or later end in organic disease. Southey laid the seeds of that disorder which terminated in the loss of his intellect, by watching at the bedside of his sick wife during the night, after the excessive literary labors of the day.[121] Newton’s mind also suffered in the later years of his life through deprivation of sleep;[122] and Dr. Forbes Winslow, in remarking on Southey’s case, says: “No brain can remain in permanent health that has been overtasked by nightly vigils still more than by daily labor.”[123] Renaudin,[124] in a very philosophical essay, calls attention to the fact that persistent wakefulness is sooner or later followed by insanity; and Maury[125] states his opinion to the same effect. The remarks of Dr. Ray[126] upon this subject are so apposite that I reproduce them in part, commending at the same time the little book from which they are taken to the attention of the reader.