80 DISEASES OF POUI.TRY. 



PARALYSIS OF THE CROP, IMPACTED CROP, OB- 

 STRUCTED CROP. 



The crop may be overloaded with dry grain, and its 

 thin muscular walls distended, exhausted and paral- 

 yzed so that the organ can not be emptied ; or, the 

 opening into the lower portion of the oesophagus may 

 be clogged with dry leaves, feathers, straw, and other 

 indigestible substances swallowed by the bird; or, 

 finally, the walls of the crop maybe paralyzed in some 

 diseases, as, for instance, in cholera and diphtheria, 

 and, as the bird continues to eat, this receptacle be- 

 comes over -distended and packed solidly with food. 

 In these different cases the symptoms are almost iden - 

 tical and the treatment must be conducted on the same 

 principles. It is convenient, therefore, to group these 

 different conditions together and consider them for 

 practical purposes as constituting one disease. 



Causation. — Improper feeding is to a great extent 

 responsible for impaction of the crop. Birds that are 

 half starved or that have had no grain for a long time 

 are liable to eat too much if they at once have access 

 to a large quantity. Again, birds which have con- 

 tracted catarrh of the crop from improper treatment 

 frequently have depraved appetites and may fill the 

 crop to repletion with food and all sorts of indigestible 

 substances. It appears, therefore, that, with the ex- 

 ception of those cases of paralysis due to the poison 

 developed in the course of the contagious diseases, and 

 of those cases of obstruction resulting from the acci - 

 dental swallowing of pins, nails, large pieces of dry 

 bones, pieces of thread or cord and similar substances, 

 this disease is caused by irregular or improper diet and 

 a failure to maintain those hygienic conditions neces - 



