6o4 THE POPULAR SCIENCE MONTHLY. 



derangement, it may be only necessary that these microscopic cells 

 should be temporarily deprived of their normal supply of oxygen 

 through the vascular system ; or, on the other hand, a slight increase 

 in the supply of the proper nutriment or stimulus may cause the same 

 results. A simple loss of equilibrium, or change of tension in the 

 nerve-cell, may cause delirium. These abnormal physical conditions 

 may be temporary or permanent, but in either case they will probably, 

 in the future as in the past, elude the most careful observation of the 

 physician, the chemist, and the microscopist. Science has calculated 

 the vibrations of the musical chord, and measured the oscillations of a 

 ray of light, but has not estimated the vibrations of the living intel- 

 lectual nerve-cell, nor analyzed its aura which waits incessantly and 

 instantly upon its will. It has furnished no means, therefore, of de- 

 termining mathematically when the mysterious organ of the mind is 

 out of tune, or why its notes are discordant, 



2. Hitherto no one has furnished a definition of insanity which 

 will cover all of the supposed examples. Nor, considering the nature 

 of the subject, is it probable that it will ever be done. It may be 

 easy to differentiate a certain class of cases. We can say, without fear 

 of contradiction, that a raving and uncontrollable maniac is insane, or 

 that another, whose life has been uniformly consistent and harmoni- 

 ous, is sane. But this is not the class of cases in reference to which 

 our opinions are asked. They do not give rise to litigation or dispute. 

 Our opinions are only asked when there exists some room for doubt as 

 to the exact mental condition of the person in question, and who there- 

 fore occupies a position near the border-lines which separate insanity 

 from sanity ; but no legal or scientific authority has established these 

 lines. They are not indicated by broad rivers, or mountain-ranges, 

 such as form the natural boundaries between nations ; but the opposite 

 conditions here become insensibly merged, in such a manner that no 

 one can say where one ends and the other begins. One might as well 

 attempt to determine the exact limits of the auroral lights. 



Says Ray, in his classical treatise on " Mental Pathology," " One 

 source, and perhaps the principal, of the prevalent error, is the habit 

 of regarding insanity as a sharply defined phenomenon, easily sepa- 

 rated from all accompanying incidents, like an earthquake or a chemi- 

 cal action, instead of a condition arising from obscure beginnings, cul- 

 minating more or less rapidly, and declining by imperceptible steps, 

 as the darkness of night is succeeded by the light of common day." 

 In these doubtful cases the expert has to consider the possible mo- 

 tives of the individual, his hereditary tendencies, his education, social 

 influences, his previous habits, his condition as to health or disease, 

 and a multitude of other matters, all of which are to be carefully 

 weighed and balanced against each other, before he can form a cor- 

 rect judgment as to whether a certain act or line of conduct implies 

 insanity and irresponsibility or not. That there should not be exact, 



