116 



in rapidly developiug disease in the young lambs. The Twnia flmbri- 

 ato, on the contrary, slowly develops a disease which culminates in 

 older lambs. 



Life history. — The life history of Taenia expansa is only incomplete 

 in that portion of its life which it passes outside of the host. Just 

 exactly what happens to the embryo-containing egg, between the time 

 that it escapes until it is again found in sheep as a little head with 

 four suckers and a short tail-like appendage is not known, but frotti our 

 present knowledge may be inferred with a tolerable degree of accuracy. 



No one has yet been able to either develop these embryos in water 

 or to feed them and produce au infection in sheep. So it has been sup- 

 posed by reasoning from the life history of other forms of toenice, that 

 these embryos must pass a portion of their development in some of 

 the minute animals which inhabit the grass and water of sheep farms. 

 From my own studies, although I have not yet been able to produce 

 tape- worm disease by feeding the embryos, I think that the above view is 

 fallacious, and that these embryos need not pass any of their existence in 

 other invertebrates. Dr. F. A. Ziirn {Die Sclimarotzer, p. lOi, 1882) is 

 authority for the statement that " the disease is also present in sheep 

 which have been fed entirely in the stalls, though more especially 

 among the younger and youngest of a herd which are sent to the 

 pastures." 



Experiment to demonstrate method of infection. — About the middle of 

 May, 1888, six lambs, from three to four months old, were bought on 

 the market and added to the flock at the Experimental Station of the 

 Bureau. This flock was kept in a small stable with an adjoining hill- 

 side yard. They were fed on clover and grain from the market, and the 

 water was drawn from a well near at hand. The yard was sufficiently 

 large to be grassy, but they soon ate it down to the roots. In one cor- 

 ner of an adjacent pen was an iron trough, kept full of water. After 

 a rain the water might have stood in the yard for a day or two in a 

 small puddle, but there was no so-called permanently standing water 

 which could have harbored insect life. There were already on the 

 place three lambs, with their mothers, which had been raised there that 

 season. 



May 16. — Two lambs were fed by drenchiug with the embryos or eggs of Twnia ex- 

 pansa. 



May2i. — Au irou trough was prepared with ii grass bottom, aud. then filled with 

 water. A qiiautity of segments of T. expaiisa were scattered iu it, aud at first ouly 

 two of tlie lambs were allowed access to it. Afterwards, all were allowed to go aud 

 drink out of it. 



June 11.— Slaughtered cue of the lambs, which had been drenched with T. mpansa 

 embryos May IG, aud had since been held iu the yard with the trough prepared on 

 May 23. No imniai were found. The experiment was thereforp of negative value. 



After these dates the lambs were neglected, so far as feeding experi- 

 ments were concerned, until fall. 



June 21.— Oue of the experimental lambs, which had previously been fed with ripe 

 segments of T. exjpmaa, -was killed. It was in poor condition, ISfo tcenla, were found 



