SYMPTOMATOLOGY OF ANIMAL 

 INSANITY. 



CHAPTER IV. 



FOEMS OP MENTAL DEFECT AND DERANGEMENT. 



CERTAIN, at least, of the lower animals are subject to the 

 same forms of mental defect or want, the same sorts of de- 

 struction or perversion total or partial of intelligence, the 

 same kinds of mental derangement, as man. There is, indeed, 

 a wonderfully close parallelism, as was long ago pointed out 

 by Pierquin and Levrat, between the mental defects and dis- 

 orders of man and those of other animals, considering the 

 very great difference in structure and habits. 



The prevalent forms of mental defect and disorder that 

 exist equally in man and other animals may be roughly but 

 conveniently divided into 



1. Those which are congenital, which appear at birth; 

 and 



2. Those which are developed subsequently to birth, 

 usually in maturity. 



These two great classes of morbid mental or moral 

 peculiarities have certain characters which place them in 

 considerable contrast to each other. As a rule, the defects 

 or disorders of the first class are life-long, confirmed, per- 

 manent and incurable; while many of those of the second 

 class are of limited duration and curable. 



Congenital mental defect includes all forms of want of 



