60 



The Rot in Sheep. 



of feeding close to the ground, and its being a ruminating 

 animal. Other external causes are also to be regarded as 

 essential adjuncts in the production of rot ; these being an ele- 

 vated temperature and an excess of moisture. Under these circum- 

 stances myriads of cercaria?, which would otherwise perish, are 

 brought to perfection, abounding wherever the ova of flukes may 

 have been conveyed. Lands liable to flood are therefore the most 

 dangerous, as the overflowing of rivers and brooks brings upon 

 them encysted cercariae in countless myriads. The danger 

 increases in proportion as the soil of such land is of a tenacious 

 character, and especially if the water accumulates in places and 

 becomes stagnant. Nor can we wonder at any land of ordinary 

 elevation, if retentive of moisture, springy, and undrained, being 

 " liable to give the rot" in wet seasons. 



No limit can be put to the existence of cercaria?, where 

 excess of moisture abounds. They may be conveyed hither in 

 forms more or less of mature development and by innumerable 

 means, some of which would be scarcely suspected. In con- 

 sidering such causes, the long duration of the vital principle 

 in the ova of the liver-fluke, of which notable examples have 

 been given, must not be lost sight of ; nor must the fact 

 of the millions of ova which are constantly being cast from 

 out of the intestines of rotten sheep and other animals, in all 

 conceivable situations and under every variety of circumstance, 

 be forgotten. 



The more we reflect on the true cause of rot and on the facts 

 connected with an outbreak of the disease, and endeavour to 

 interpret them by our knowledge of the natural history of the 

 liver-fluke, the more simple and easy of comprehension does 

 the whole subject become. In the course of these pages many 

 proofs are given of the correctness of this position ; but, as we 

 are unwilling to add to such evidence, we pass on to record 

 several instances of the quick contamination of sheep with 

 the disease. 



Quick Contamination. 



The attention which has been given by practical observers to 

 the several circumstances under which rot shows itself, long 

 since proved that the disease could be quickly engendered. 

 Many such instances are recorded, some of which we purpose to 

 give in extenso, as thereby additional confirmation will be 

 afforded of the correctness of our statement that rot is exclusively 

 an entozoic disease. 



As early as 1636, allusion is made to the subject by Crawshey, 

 who remarks that " many shepherds say that, if the weather be 



