Different views in relation to the influence of consanguinity-- The customs of the ancient Egyptians, Syrians, and others-- Experiments in the inter-breeding of cattle--Popular impressions as to its effects--Opposite views explained by understanding the laws of heredity--Favorable as well as unfavorable tendencies are increased--Hence unfavorable ones may be eliminated 145 CHAPTER X. ALCOHOL. General considerations concerning its effects upon the nervous system--Its use at the present time as compared with that of the past--Society now reaping the effects of its use in the past--Physiological effects of alcohol upon the system-- Experiments of Dr. Parkes and Count Wollowicz--Its effect upon the action of the heart--Its effect upon the circulation of the brain, the blood-vessels, and cells, resulting in a less sensitive condition of these parts, and ultimately in organic changes--Its effect upon the character of mind; upon the electrical currents of the brain; upon other portions of the body; upon the brains of children and young persons--The alcoholic diathesis likely to be transmitted 153 CHAPTER XI. TOBACCO. Opposite views as to its general effects upon individuals--The physiological effects upon the mucous membranes, the heart, and the nervous system--Nicotin--Its elimination from the system by the lungs, skin, and kidneys--Its effects those of a narcotic and not of a stimulant--Its effects upon the brains of children and young persons--The use of tobacco by children should be forbidden by law--Its general effects upon society, socially and politically, as presented by M. Fiévée--It is not directly responsible in any large degree for producing insanity--Creates a diathesis which causes a diminution of intellectual and moral power 173 CHAPTER XII. SEX IN RELATION TO INSANITY. Relative frequency of the occurrence of insanity in the sexes-- The sexual system in the female exerts a larger influence upon the nervous system in certain ways than that of the male-- Sexual derangements dependent upon the debility of the nervous system--They are generally _consequents_ and not causes of nervous debility--Functional derangements of sexual organs rare among the insane--A tendency to recovery in case they do exist--Other conditions not favorable to mental health 187 CHAPTER XIII. POVERTY.