CHAPTER XVI. 



PHYSICAL CAUSES OF MENTAL DIFFERENCE AND DISOEDEE. 



III. General* 



WEATHER CHANGES, atmospheric influences, produce in 

 certain animals excitement, passing sometimes beyond the 

 bounds of control ; in others, depression of spirits, of the 

 character, in a minor degree, of melancholia. The feeling 

 of coming weather-change is expressed in some animals by 

 agitation, inquietude, bellowing, or other voice-sounds ; in 

 monkeys by excitement, characterised by, or consisting of, 

 laughing, dancing, and leaping, followed even by eroto- 

 mania, according to Pierquin, who speaks also of climatic 

 influences producing insanity in the dogs of Kamtschatka. 



Of atmospheric influences solar heat, if prolonged or 

 intense, undue exposure to hot weather, causes sensorial dis- 

 turbance, delirium, general irritability sometimes amounting 

 to a kind of frenzy, even to mania, in the horse (Pierquin). 

 Heat of weather causes excitement, irritation, irritability, or 

 rage in bees (Watson, Figuier, and Lubbock), and associated 

 therewith a dangerous liability to sting. It is in a condition 

 of irascibility so produced sometimes in wasps that they, 

 like bees, are apt to sting human internieddlers with their 

 freedom. Mrs. Burton describes the heat of Syria as a 

 cause of madness meaning apparently thereby ordinary 

 mania in English pet dogs there ; for she expressly states 

 separately that 'mad dogs are here unknown' no doubt 

 meaning rabid ones. In the same country and under the 

 same circumstances such dogs perish also of ' decline, 5 

 without madness. One, she says, 'withered away in a 



