10 



BULLETIN 597, TJ. S. DEPARTMENT OF AGRICULTURE. 



during the time when larvae were naturally dropping with excreta. 

 The numbers do not show the maximum infestations of larva? that 

 may have been present. Many of the dead horses examined had 

 been subjected to various environments prior to the autopsies and are 

 not representative of infestations found when horses have spent the 

 entire previous summer in pastures. 



Table I. — GfastrophUus findings in post-mortem examinations of horses at Aber- 

 deen. S. Dak.. 1915-16. 





Spent summer. 



Larvae in 



stomach. 



Larvae in duoden 



urn. 



ii 



C3 ~ 

 ffl - 



•- — 



-- = 



E = 



SJ3 



a 

 > 



Horse 

 died. 



■A 



s 



00 



H 

 =. 



i 



it • 



C CO 



I! 



— 



DO 



= 



'■= = 



— = 

 O ~r 



■A 



1 



O 



= 



"3 

 a 



6 



i 



s- • 



ll 



^ - 



S-l 



c 



1 



a 



1915. 

 June 7 





295 

 158 



103 



5S 



33 



18 



6 



11 

 *"290' 



21 

 12 



1 

 3 











9 

 14 



1 337 



July 8 

 July 14 

 Julv 21 

 July 26 

 Aug. 12 

 Aug. 23 

 Aug. 23 

 Aug. 26 

 Aug. 26 

 Aug. 26 











184 







11 



l 







116 











351 













1 



34 



do 















18 



do 







10 

 67 

 35 

 71 

 42 

 217 

 101 











16 



In pasture, 1915 



















9 

 5 



1 











Ad 











76 



















42 



Sept. 13 

 Sept. 17 

 Sept. 20 

 Sept. 21 

 Oct. 1 



Countrv and town driving . 



















217 

















71 

 22 



13 



^2 





172 



Driven on streets 

















22 



.... do 



1 



6 



123 

 7 

 56 

 44 

 64 

 18 

 16 

 3 



687 

 72 



116 

 92 



461 



151 

 39 

 20 





4 

 50 









IS 



Farm work 











13S 



1916. 

 Mar 20 

 May 20 

 May 29 

 May 29 



do 



15 



7 









145 





















1 

 10 



10 

 35 















67 









22 



5 



19 









111 









2 







71 









5 



1 







42 

















17 





Driven on streets 















3 



June 26 





70 

 2 

 2 

 5 





7 



178 



137 







89 



2 1.032 





.-. . . .do .' 



26 









237 



Julv 11 



Farm work 







19 

 144 

 149 



1 







138 



Julv 17 



do 









241 



July 24 

 Aug. 3 

 Aug. 4 

 Aug. 7 

 Aug. 6 

 Aug. 11 











610 



Farm work 



1 

 16 



1 

 4 









153 







4 



30 

 25 

 1 







93 





2 



1 



47 









13 





: 



14 





24 



29 



1 



44 



1 



2 



5 

 2 











24 



Aug. 11 

 Aug. 23 





14 



1 







4 









4s 





6 



S 









26 

 16 

 12 





33 



Aug. 23 









8 





26 



102 



Aug. 26 





36 



Sept. 1 

 Sept. 8 

 Sept, 11 

 Sept. 16 









20 

 1 





21 







1 



1 





14 





1^ 





6 









37 





31 





70 











. 





1 Includes 1 G. intestinalis temporarily attached in colon. 



2 Includes 1 G. intestinalis temporarily attached in rectum. 



LARVAL MOVEMENTS WITHIN THE HORSE. 



TVTien a post-mortem examination is made, the larva 3 usually are 

 found quiescent, although occasionally some may be observed to move 

 the posterior end slightly. The smaller larva? show more activity 

 than do well- developed ones. 



