The Rot in Slicrp. 
77 
To show tliat uj) to this j)cni()(l little; more was known on the 
Continent with relbronco to the subject than among ouisc^lves, 
we may here state that MM. Hamont and Fischer, whose in- 
vesti}j;ations have been previously referred to {j)af/c 60), aflirm that 
" all the veterinary surgeons of Europe agree with regard to the 
exciting causes of rot. Chabert, Dupuy, Hurtrel D'Arboval, 
&c., describe its prevalence in low situations ; the feeding on 
marshy plants, as the different species of ranunculus, or plants 
which grow in or under water ; the drinking of stagnant waters 
filled with insects, or where the fluke-worm and the leech abound ; 
the infected air of the sheepcote, and the sudden change from 
dry to green food." MM. Hamont and Fischer, however, com- 
bat most of these opinions, and conclude by asking " whether the 
rot may not be an essential disease, dependent on a primitive 
alteration of the blood, due to watery food ? " 
The Arabs, they state, attribute this disease to the sheep feed- 
ing on a tender rushy grass, which they call dysse : — 
"As soon .IS the waters of the Nile begin to subside, tlie jiastiires are covered 
with dyxse. The sheep are exceedingly fond of it, and they are permitted to 
feed on it all day long, their feet being buried in the mud ; and, as we have 
already said, for many months they have no other aliment. In the course of 
a veiy little time they begin to get fat, when, if possible, they are sold. Their 
flesh is then exceedingly delicate ; but soon after this the disease begins to 
appear, and the mortalit}^ commences. 
" In the neighbourhood of Abou-Zabel there is a vast tract of low land 
which the Nile overflows for two months. When the waters retire, it is found 
to be covered with these rushes. The neighbouring inhabitants hasten to drive 
their flocks thither, and they leave them on the marsh from the rising to the 
setting sun. Every year the rot carries oft' numerous victims ; but it is a 
matter of general remark, that this disease is more frequent and fatal when 
the sheep are first turned on the newly-recovered pasture, than afterwards 
when.tlie ground has become dried and the rushy grass harder." 
We come now to a theory of the cause, which ought not to be 
too hastily rejected. It is founded on a knowledge of the man- 
ner in which many entozoi'c worms are propagated, naviehj, 
directly by ova, which produce young Avorms precisely like the 
parent. Long prior, however, to the period we are now alluding 
to — 1836 — it was well known to scientific inquirers that the 
liver-fluke was an oviparous creature, and that it deposited 
an enormous number of eggs {see fig. 9) within the biliary 
ducts. It had also by some practical Avriters on the diseases of 
sheep been stated that flukes might originate from the eggs of 
" sovic insects " which had been deposited on the herbage, par- 
ticularly of wet soils. Others, however, far better informed on 
natural history, suggested that the existence of the fluke in the 
liver was probably due to the ova of the parasite being con- 
veyed into the digestive organs of the sheep while feeding on 
