ON THE PROPAGATION OF ROT IN SHEEP. 
99 
Sixthly.— If we dwell upon the character of the egg, upon its 
habits of vitality ; if we find that desiccation, or warmth without 
moisture, deprives the egg of rotundity, and probably of vi- 
tality ; if, by such process, eggs become ruptured, flattened, or 
collapsed, so as to appear more like a boiled pea that has grown 
cold than a plump egg ; if we find that some of the eggs so 
treated, probably those in which vitality was not quite extinct, 
became on the addition of water only replumped and apparently 
restored to health, we shall be led to infer that those eggs which 
are eliminated from sheep’s dung by hasty rain will perish from 
desiccation ; if the soil be porous, sandy, and gravelly, through 
which the water can filter, leaving the eggs upon the surface ; 
whilst, on the other hand, if the soil be compact loam or clay, 
through which water cannot easily percolate, but is compelled to 
find its level upon the surface, these eggs will be rolled, and 
floated by the little currents, and escape desiccation. Hence, 
one will be called sound and the other unsound land for sheep 
pasture. But even sound pasture, whilst fed upon by an unsound 
flock, may sometimes appear unsound upon an admixture of 
sound sheep : the splash of a large drop of hasty rain must ne- 
cessarily scatter many eggs in several directions, and some of 
these may fall upon the crown of a grass plant ; also temporary 
puddles, in which foul excrement is dissolving, may convey eggs 
into the crown of a grass plant, and these may be pushed up by 
hasty growth, so as to enable hard-fed sheep to nab them with 
the young blade before desiccation shall have destroyed their 
vitality. 
Seventhly. — If we discover that cold frost as well as desicca- 
tion destroys the vitality of these eggs, we shall at the same 
time have ascertained whence arises the sweetening effect of 
hoar-frost and wintry weather to render unsound pasture sound. 
In short, if we call to mind and dwell upon the habits of vitality, 
the abundance, &c. of flukes’ eggs, we shall cease to wonder at 
any thing that has ever been stated with an air of mystery in 
regard to the propagation of the disease called rot : the only 
mystery is, that we have alive one head of sheep in Britain. 
I have collected many millions of the eggs of the fluke from 
the gall vessels of diseased sheep, in the manner previously de- 
scribed. I put several parcels of these eggs in paper for future 
examination ; and I carried some of them in my pocket from 
Blackthorn, Oxon, the scite of my experiments, to London. 
About two years ago, I delivered one parcel to Mr. Carpenter, 
of Regent Street, of whom I bought my microscope, and who I 
hoped would feel interest enough in the thing to subject them to 
an examination before his very powerful solar microscope, and 
