MOBTALITV AMONG WATERFOWL. 5 



into a chalky mass which closed the anal opening. In about one- 

 third of the birds kept under observation a secondary trouble de- 

 veloped in the course of two days or more after they lost the power of 

 flight. A watery exudate came from the eyes and nasal chamber, 

 and through the internal nares ran into the throat. This occasioned 

 trouble in breathing. At times the discharge thickened into a whit- 

 ish, cheesy mass and cemented the eyelids together. 



THEORIES AS TO CAUSE. 



Many theories have been advanced to account for the mortality. 

 It has been variously ascribed to bacterial infection, typhoid in- 

 fection from the presence of sewage, parasitic nematodes, poisoning 

 from the deposition of sulphur or arsenic from smelters, and waste 

 water from sugar factories. Other minor hypotheses need not be 

 noted. 



BACTERIAL INFECTION. 



The fact that so many species of birds are affected militates against 

 the theory of bacterial infection, and no bacillus apparently capable 

 of transmitting the trouble has been isolated. Dr. J. R. Mohler, 

 of the Bureau of Animal Industry, writes as follows concerning the 

 ducks examined in that bureau : 



Relative to our investigations concerning the cause of death of large numbers of 

 ducks in Utah, the information at hand points to the probability that death is due to 

 an acute poisoning, and not to a disease of bacterial origin. The suggestion has fre- 

 que.i^y been made in the past that the water which the ducks drink is poisoned by 

 the discharge of sulphuric acid, arsenic, copper, and other materials from smelters. 

 A duck in captivity can be easily poisoned by administering any of these substances; 

 but it is very doubtful whether a large body of running water in which large numbers 

 of ducks in flight could obtain water could be poisoned even if a large chemical works 

 discharged its entire output into the stream. Dilute sulphuric acid in small amounts 

 is harmless, and it is doubtful whether ducks would drink a solution of sulphuric 

 acid of any appreciable strength because of the sour taste. Estimations were made of 

 the amounts of sulphates, sulphuric acid, arsenic, and copper in the stomach contents 

 and tissues of ducks from Utah. In no case did the results obtained point to any of 

 these substances as the probable cause of death. Small amounts of sulphates, arsenic, 

 and copper can be found in the tissues of any animal, and are no indication of abnormal 

 conditions. 



Practically all the live ducks forwarded to Washington for study promptly recovered, 

 while the dead ducks received were autopsied, but failed to show lesions of diagnostic 

 value. Numerous inoculations were made from the different organs of the ducks, both 

 on culture media and into experimental animals, but up to the present no special 

 organism has been found which might be regarded as the causative agent of the disease. 

 The earlier incrimination of the coccidia found in the intestinal canal of a number of 

 ducks, as the exciting factors of the disease, has not been substantiated by later 

 investigations. 



PARASITIC NEMATODES. 



Microscopic examinations in the field of a large number of blood 

 smears failed to reveal the presence of nematodes, and a collection of 

 material from the feeding grounds of the ducks near the mouth of the 



