168 REPORT OF THE BUEEAU OF ANIMAL INDUSTRY. 



Mrs. Mary L. Givens, who. at great inconvenience to herself, did all 

 in her power to aid me. In the spring of 1887 I again visited Col- 

 orado Springs and prosecuted other experiments, which it was hardly 

 possible to conduct in the East. 



Early in my investigations I began to recognize the fact that one 

 tsenia, which I have identified as Tcenia fimbriata, Diesing, was the 

 most abundant; that it was scarcely ever absent in sheep examined, 

 and was the probable cause of most of the tape-worm disease of 

 Western sheep. As this tsenia was so constantly present, I soon 

 directed my attention to it, and endeavored to obtain it in all of its 

 stages, and to learn how and where it passed its entire life. I soon 

 learned another fact, that the other species of tape- worm ( Tcenia ex- 

 pansa), usually abundant in lambs, was found so infrequently that I 

 would be unable to find sufficient material for study. The methods of 

 study were, first, observation, and, second, experimentation. The ex- 

 periments have, as yet, been productive of nothing but negative re- 

 sults. In determining so much of the life history as has been learned, 

 post mortem observations have been the most useful. Not only 

 have animals been slaughtered on the ranch for this purpose, but ad- 

 vantages offered by inspections of sheep slaughtered at the shambles 

 for consumption have been utilized. From these inspections the 

 abundance of the parasite, the first appearance in lambs, the differ- 

 ent stages in growth, etc. , could be learned, but it soon came to be 

 necessary to study the surroundings of the sheep the corral, the 

 watering places, and the range to learn under what condition the 

 parasite must exist while external to the sheep, i. e., while passing 

 from sheep to sheep. 



The effects of the parasite on its host (the sheep) were arrived at 

 from studies of the flocks and from observation of individuals at 

 post mortems. The changes found were noted and careful attention 

 paid to the point whether certain changes were due to parasites or 

 another disease called " loco." As all of the sheep examined were 

 called "locos," it is evident that there was here a source of error. 

 No certain pathognomonic lesion of "loco" was learned; as all of 

 the " locos" were infected with tseniye, the separation of char- 

 acters due to each disease was difficult. Indeed, it has seemed to me 

 that all of the symptoms due to the parasitic disease may be ascribed 

 to loco. The characters of the tape-worm disease are, however, well 

 marked in lambs which have never learned to eat this weed ex- 

 clusively, and thus could be studied without regard to "loco," 

 which, if a disease at all, belongs to yearlings and older sheep. 



Experiments were undertaken with a view of infecting lambs with 

 the parasites, while the lambs were kept from other possible sources 

 of infection; but these were fruitless. Other experiments were en- 

 tered upon with a view of removing these parasites by medicinal 

 remedies. None of these were effective in removing the parasites 

 from the gall ducts, and were abandoned until more could be learned 

 of the life history of- the parasite, when they could again be taken up 

 with perhaps a better prospect of success. 



The total results regarding this tsenia, so far obtained, are as fol- 

 lows, viz: 



The parasite persists in an adult stage in the older sheep through- 

 out the year. 



The smallest forms appear in lambs soon after the second month 

 of their age, and may be found in sheep of any age throughout the 

 year, excepting, possibly, the winter months. 



