120 
Tlie Rot in Sheep. 
Zuricli." Mr. Fox, of Topsliam, Devonsliire, also found one 
beneath tlio skin a little beliind the ear o{ a sailor, which appa- 
rently in no way differed from the ordinary liver-fluke. Rightly 
considered, these cases tend to prove that the natural history of 
the liver-fluke is identical with that of others of the class. 
To pass from these exceptional cases of development of flukes 
again to those of the sheep, we would repeat that the two causes 
which render this animal so remarkably susceptible to the en- 
tozoon, are its natural habit of feeding close to the ground and 
its being a ruminating animal. In the production, however, of 
rot, external causes are the chief in operation ; these being an 
elevated temperature combined with excess of moisture. Under 
these circumstances 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 there- 
fore the most dangerous, as the overflowing of rivers and brooks 
brings upon them these infusorial creatures in countless numbers. 
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 un- 
drained, being " liable to give the rot," 
No limit can be put to the liabilities of the presence oi cercarite, 
where excess of moisture abounds. They may be conveyed in 
some of their metamorphoses, and in forms more or less active, 
by innumerable means, some of which would be scarcely 'sus- 
pected. In considering these 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. 
The more we reflect on the true cause of rot and on the facts 
connected with its appearance, and endeavour to interpret these 
by our knowledge of the natural history of the liver-fluke, the 
more easy of comprehension and simple does the whole subject 
become, till at last we see no ambiguity whatever belonging to it. 
In the course of these pages many proofs are given of the correct- 
ness of this position ; but, as we are unwilling to multiply these 
without suflicient reason, we shall pass on to record, in the next 
place, several instances of the quick contamination of sheep with 
this disease. 
Quick Contamination. 
The attention which has been given by practical observers to 
the several circumstances under which rot shows itself, long since 
