116 



iu rapidly developiuj? disease in the young lambs. The Taenia fimhri- 

 ata, on the contrary, slowly develops a disease which culminates iu 

 older lambs. 



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

 in that i)ortiou 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 sheej) as a little head with 

 four suckers and a short tail-like ai)pendage is not known, but from 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 an infection in sheep. So it has been sup- 

 posed by reasoning from the life history of other forms of twnice, 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, altliough 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 iu 

 other invertebrates. Dr. F. A. Ziirn {Die Schmarotser, p. 191, 1882) is 

 authority for the statement tliat " 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." 



Uxperiment 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. Tliis 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 sufllciently 

 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 iu the yard for a day or two iu 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 drenching with the embryos or eggs of Tania ex- 

 pansa. 



May 22. — An iron trough was prepared with a grass bottom, and then filled with 

 water. A quantity of segments of T. expansa were scattered iu it, and at first only 

 two of till! lambs were allowed access to it. Afterwards, all were allowed to go and 

 drink out of it. 



Jitiic 11. — Slaughtered one of the lambs, which had been drenched with T. expansa 

 embryos May 1(5, and had since been held in the yard with the trough prepared on 

 May 22. No iu'iiicB were found. The experiment was therefore of negative value. 



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

 ments were concerned, until fall. 



</ttne 21. — One of the experimental lambs, whioh had previously beon fed with ripe 

 eegmeuts of T. expansa, was killed. It waa 1 a poor c(uiditioa» J{q Wnm were found 



