176 DISEASES OF POULTRY. 



of eight weeks. It is not surprising, therefore, that, 

 although birds have so few parasites upon them when 

 well cared for that these insects can not be discovered, 

 a few weeks of neglect and unfavorable surroundings 

 may bring an entire change and reveal them covered 

 with vermin, exhausted and emaciated. 



It is not many years since there was a general belief 

 in the spontaneous generation of lice from accumula- 

 tions of dirt and filth, and a remnant of this belief 

 still lingers in many minds. We may now safely 

 banish any tendency to this antiquated theory which 

 we may have inherited or ac- 

 quired through the influence of 

 tradition. The theory of spon- 

 taneous generation was first ex- 

 ploded as applied to crocodiles 

 and reptiles of the tropical 

 swamps and rivers ; still later it 

 was shown to be untrue with re- 

 gard to lice and other insects, and 

 finally it was disproved in rela- 

 tion to the very smallest organ - 

 'Pig.w.—Lipenruscoiumbae. isms that are revealed by the 

 , igeons. highest powers of the microscope. 



Today it is admitted by all scientists that every living 

 thing is descended from a living parent of the same 

 nature. 



The different species of lice and mites are as easily 

 distinguished from each other by experts as are the 

 different species of birds. Their peculiarities are in - 

 heri ted from generation to generation, and they con- 

 tinue to live upon the same species of birds. The 

 hens, the turkeys, the pigeons, the ducks, the geese, 

 and the Guinea fowls each have their peculiar species 



