CHAPTER II. 

 DISUSE AND ITS EFFECTS. 



DISUSE of a part usually leads to its enfeeblement and 

 diminution, a result conveniently expressed by the term 

 atrophy ; in many instances the effects of disuse are 

 transmitted. Atrophy may be induced in a variety of 

 ways, but in nearly all cases it is attributable to 

 diminished use and its inevitable consequence, lessened 

 blood supply. Disuse of a part may be caused by 

 changed habits of life, or by the increasing importance 

 of some other organ. Certain parts are only useful for 

 a brief period in an animal's life ; some appear to have 

 no function and are present in conformity with the law 

 of heredity, whilst atrophy from disuse may be the 

 consequence of injury ; and, lastly, an interesting variety 

 of atrophy is due to continuous pressure. It will there- 

 fore be instructive as well as conducive to clearness to 

 describe some typical cases of the various forms of 

 atrophy. 



Atrophy from changed habits. Among the many 

 anomalies of animal life in New Zealand must be in- 

 cluded the remarkable owl-parrot or kakapoe (Stringops 

 habroptilus}. This bird is nocturnal in its habits, feeds 

 on fern-shoot, roots, berries, and, it is said, occasionally 

 lizards. It climbs but does not fly, though possessing 



