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UNITED STATES DEPARTMENT OF AGRICULTURE 

 BULLETIN No. 817 



Contribution ttom the Bureau of Animal Industry 

 JOHN R. MOHLER, Cliief 



Washington, D. C. PROFESSIONAL PAPER May 12, 1920 



OBSERVATIONS ON THE LIFE HISTORY 

 OF ASCARIS LUMBRICOIDES 



By 



B. H. RANSOM, Chief, and W. D. FOSTER, 



Junior Zoologist, Zoological Division 



CONTENTS 



Page 



HlBtorical Summary 1 



Probable Identity of Aacaria lumbrtootd«s un^Aacaria auurn . A 



Esg Stage otAscaria ... - i 



Larval Stages of Ascar;« 10 



Relation of Age to Aacaris Infestation , , 24 



Aacaria Pneumonia . 27 



Longevity of Larvae Outside tlie Host 29 



Natural Occurrence of Ascarte in Sheep 29 



Life History of Related Nematodes 30 



Details of Experiments with Aacaria . 31 



General Summary 43 



Bibliography 4S 



WASHINGTON 

 OOVERNMENT PRINTING OFFICE 



1920 



