118 



ill the experiment segments of tape-woniis were placed in an iron trough 

 ont of which the sheep drank, or could have drunk all suinmer lon<; ; 

 and there might have been times when, for a day or two, aiittle puddle 

 of water could have collected after a rain. In these, more especially 

 the former, the development of the parasites could have proceeded 

 until they were taken up by the lambs. The point in doubt is, whether 

 the lambs got their embryos from the water or from the yard while 

 grazing. I am inclined to believe the latter, for they acquired other 

 species of worms which were not placed in the iron tank, and these were 

 also in various stages of development. Still another feature inclines 

 me to this view. If the lambs had been infected from the iron tank 

 they would very likely have been infected by a large number of /rt'nw, 

 all of nearly equal size; but they were not. Direct infection has been 

 tried before, but only negative evidence obtained. The failures prob- 

 ably arose not only from expecting results too soon, but also from not 

 preparing the infecting material ]n-operly. 



Since writing the above, two lambs have been examined, which give 

 additional data : 



Aufiust 10, 1889. — A five montlis old lamb wns examined, which had been born at 

 the experimeutal station, and kept there nnder the same conditions as the other 

 lambs, i. e., water snpplied from a pump and pasturage from tlie yard and lane near 

 the sheep pens. This lamb coutaiaed two adult Tivniae, and SlrorujijUis contortus, S. 

 flicollis, S. ventricosus, Dochmius cer7mits, TrichocephaJu's affitiis, and (Esojphagostoma 

 Cohnnbianwm, iu all stages of growth. The last species did not show adults. 



August 10. — Examined a lamb eleven weeks old, which bad been bought with its 

 mother from a neighboring slaughter house when two days old. Tlie lamb bad been 

 kept under the same conditions as above. There were found one adult Tivnia (shed- 

 ding proglottides carrying well-developed six-hooked embryos) and all the other 

 species enumerated above, but not in the same abundance. Each of these lambs 

 showed that the infection had been continuous. Tlie elder of the two yielded a 

 greater number of S. filicoUis than auy sheep hitherto killed, and led me to think 

 that this species may have been productive of more trouble than had hitherto been 

 suspected. 



The above experiments were planned with an aim to obtain infection 

 within a limited area, and nnder conditions which could be controlled, 

 deeming it better to obtain infection nnder such conditions, though 

 there be a number of them to complicate the question, than to restrict 

 the conditions and not get an infection. 



The presence of the adult twnla in the comparatively young lamb of 

 eleven weeks shortens the limit of time of complete development of the 

 frvnia. The tfvnia was about two yards long, and had developed inside 

 of three montlis. A reason for the early infection of this lamb was that 

 its mother died and left it to shift for itself. These experiments con- 

 clude the series for determining whether sheep necessarily getthe worms 

 from drinking water or from the jiasturage. 



i:iummary. — Tlie life history seems from the above to be a compara- 

 tively simple affair. The embryos pass from sheep to sheej) and develop 

 into adults, which reproduce young for infection of other animals. 



