CHAP ER Th 
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 (S¢ringops 
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 
