UNITED STATES DEPARTMENT OF AGRICULTURE 
inka hh No. 817 | 
Contribution from thé B pin i Inditstry 
JOHN, R. * 
- es &. 
% 
Washington, D. C. eT | May 12, 1920 
aI 
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4 \ ye + 
OBSERVATIONS ON THE LIFE HISTORY 
OF ASCARIS LUMBRICOIDES 
By 
B. H. RANSOM, Chief, and W. D. FOSTER, 
Junior Zoologist, Zoological Division © 
CONTENTS 
Historical Summary . . . ». «3 « Sate 
Probable Identity of Ascaris lumbricoides and Ascusta suum 
EggStageofAscaris. . . . «» 
Larval Stages of Ascaris . . 
Relation of Age to Ascaris Infestation 
Ascaris Pneumonia . . . 
Longevity of Larve Outside the Host 
Natural Occurrence of Ascaris in Sheep 
Life History of Related Nematodes . 
Details of Experiments with Ascaris 
General Summary SN ie 
Bibliography eet Sait) 
WASHINGTON 
GOVERNMENT PRINTING OFFICE 
1920 
