118 ZOOLOGICAL PHILOSOPHY 



with their need of crawling, and very short legs would have been 

 incapable of moving their body, since they could only have had four. 

 The disuse of these parts thus became permanent in the various races 

 of these animals, and resulted in the complete disappearance of these 

 same parts, although legs really belong to the plan of organisation of 

 the animals of this class. 



Many insects, which should have wings according to the natural 

 characteristics of their order and even of their genus, are more or less 

 completely devoid of them through disuse. Instances are furnished 

 by many Coleoptera, Orthoptera, Hymenoptera and Hemiptera, etc., 

 where the habits of these animals never involve them in the necessity 

 of using their wings. 



But it is not enough to give an explanation of the cause which has 

 brought about the present condition of the organs of the various 

 animals, — a condition that is always found to be the same in animals 

 of the same species ; we have in addition to cite instances of changes 

 wrought in the organs of a single individual during its life, as the 

 exclusive result of a great mutation in the habits of the individuals 

 of its species. The following very remarkable fact will complete the 

 proof of the influence of habits on the condition of the organs, and of 

 the way in which permanent changes in the habits of an individual 

 lead to others in the condition of the organs, which come into action 

 during the exercise of these habits. 



M. Tenon, a member of the Institute, has notified to the class of 

 sciences, that he had examined the intestinal canal of several men who 

 had been great drinkers for a large part of their Uves, and in every 

 case he had found it shortened to an extraordinary degree, as compared 

 with the same organ in all those who had not adopted the hke 

 habit. 



It is known that great drinkers, or those who are addicted to drunken- 

 ness, take very httle solid food, and eat hardly anything ; since the 

 drink which they consume so copiously and frequently is sufficient 

 to feed them. 



Now since fluid foods, especially spirits, do not long remain either 

 in the stomach or intestine, the stomach and the rest of the intestinal 

 canal lose among drinkers the habit of being distended, just as among 

 sedentary persons, who are continually engaged on mental work and 

 are accustomed to take very Httle food ; for in their case also the 

 stomach slowly shrinks and the intestine shortens. 



This has nothing to do with any shrinkage or shortening due to a 

 binding of the parts which would permit of the ordinary extension, 

 if instead of remaining empty these viscera were again filled ; we 

 have to do with a real shrinkage and shortening of considerable extent, 



