Mental depression is a very common accompaniment or symptom of the absorption of toxic materials of autogenous origin. It occurs in the pathogenesis of many of the substances described in Part II and varies in grade from slight bodily fatigue to total prostration and depression insanity. Two classes of symptoms result from auto-intoxications, the subjective, - apathy, insomnia, somnolence, inability to concentrate the attention, headache, sense of oppression and many others of this character. The other class illustrates the more severe grade, - unconsciousness, convulsions, coma, choreiform movements, contraction of the pupils, vomiting and purging. The former class suggests the clinical features of neurasthenia, the latter those of organic disease of the nervous system, and acute poisoning. The sensations of suffocation and the dyspnea of auto-intoxication may be due to the direct irritation of the respiratory centre in the brain by the poison in the blood or lymph streams, or they may be reflex, due to the irritation of the gastric terminals of the pulmonary vagus.

The well known depression of Jaundice results from the disturbed intestinal function which necessarily ensues from hepatic insufficiency, as well as from the toxic action of the bile salts and pigments, and presents all grades from malaise and prostration to absolute insanity and melancholia. For these reasons the toxemia is not purely hepatic in character, and the more complete the suspension of liver function, the greater the probability of the addition of the intestinal element. The subjective mental symptoms of ordinarily severe cases of jaundice are those of generally depressed mentality, malaise, dull heavy frontal headache, rheumatoid pains in all parts of the body, somnolence and inability to concentrate the attention upon any subject or do any intellectual work. A patient is unable to remember that which he read or did a few minutes before, - all of which might be in terpreted as indicative of cerebral disease, did not clinical experience teach that these symptoms are but the effects of biliary insufficiency. If however the intoxication is more profound, the lassitude develops into coma which may be interrupted by convulsions, delirium, muscular twitchings and hiccough, all increasing in severity until death supervenes. This is very much the clinical picture in acute yellow atrophy. Or, the symptoms may develop into a true melancholia, which is not uncommon in hepatic disease.