CHAPTER XIY. 



PHYSICAL CAUSES OF MENTAL DIFFERENCE AND DISORDER. 



I. Physiological. 



As in man, what are called the physical causes of mental 

 disturbance are, in other animals, probably on the whole the 

 most frequent and important (Pierquin). But the relative 

 frequency and importance of physical and moral causes in 

 them have yet to be determined ; for up to the present time 

 the etiology of insanity in the lower animals has not been 

 adequately studied. 



Referable mainly to the so-called ' physical ' class of 

 causes of mental difference or disturbance in the lower 

 animals are the following : 



I. Normal or physiological bodily changes, including 

 those which are developmental ; such as 



Age. Rutting. 



Sex. Pregnancy. 



Dentition. Parturition. 



Moulting. Lactation. 



II. Abnormal or pathological conditions, which include 



1. Physical debility or degeneration, however aris- 

 ing ; such as from 



General ill-health, however induced. 

 Deficient, excessive, or improper aliment food 



and drink. 



Exhaustion of over-work, of shock. 

 Sleeplessness. 

 Bodily pain. 



2. Specific derangements or diseases of 



The blood-supply, as to its 



