202 



after which many died. Baillet (Colin, O., Bull deVAead. de Med., t 

 XXXI, 1866, p. 874) preserved them alive in water for several months. 

 Ercolani (Neumann, Traite des Maladies parasitaires, p. 515) is author- 

 ity for the statement that they can be resuscitated after being dried a 

 year by putting them in water. The writer has kept them in stagnant 

 water for weeks. Ercolani's statement is by far the most remarkable, 

 and accounts for results obtained in an experiment in which the writer^ 

 kept sheep for five months on a narrow dry pasture, supplying them 

 with water from a pump only. When these sheep were examined they 

 were found affected with Strongylus eontortus, S.filicollis, iS. ventricosus, 

 Dochmius cernuus, and Trnnia expansa in very young and old stages. The 

 eggs of these were introduced on the pasture from two or three older 

 sheep which were with the younger ones, or possibly by the young 

 sheep themselves, some of which were between three and four months 

 old at the time. Two of the lot were born and raised under experi- 

 mental supervision, and these were also infected. Strongylus filaria 

 was not present, but it was not discovered in any of the sheep from the 

 same lot killed at the time of selection of the experimental animals, nor 

 has any trace of this parasite been discovered in any of the older ones 

 kept at the Experimental Station. 



Professor Eaillet details experiments (Recueil de Mid. Vetirinaire An- 

 nexe, 7 Serie, Tome YI, No. 8, April 30, 1889, p. 173) in which he dried 

 embryos of Strongylus filaria under different conditions, and found, after 

 a few failures, that some could be revivified as late as sixty-three hours 

 afterward by placing them in water. His success depended on the 

 condition of the embryo at the time of drying. 



It may be accepted, therefore, that the young parasite may retain vi- 

 tality indefinitely, depending on telluric and atmospheric conditions. 

 From Leuekart's experiment it is to be inferred that though moist earth 

 and damp places are favorable for the life of the young parasites, yet 

 they are liable to molt and then may die from the loss of the older and 

 tougher external skin. Prom Ercolani's and Eaillet's experiments we 

 may infer that the drying of the young parasite suspends its functions, 

 which revive again when the surroundings are suitable, and that the 

 parasite is in this state the most dangerous to sheep. 



Preventive treatment. — The foregoing indicates that after a farm is 

 once infected the prevention is not an easy matter, for dry embryos 

 may be scattered everywhere. Although the parasite is more abundant 

 at some seasons, than at others, yet it may be found in limited numbers 

 at all seasons, and animals affected will distribute the eggs throughout 

 the year, thus increasing the difflculties of prevention. All animals 

 which show the least appearance of being affected should be separated 

 from the sound ones. The water supplied to the sheep should be pure, 

 i. e., either taken from wells or led into troughs from sources which can 

 hot be contaminated. If the sheep are allowed to drink from running 

 water, then all of the brook should be fenced out except where the 



