186 DADD'S VETERINARY MEDICINE AND SURGERY. 
abdumen, thorax, and cranium. Their bulk and weight often e 
ceeds that of an ordinary grasshopper ; still you see and hear them, 
skipping, jumping, and chirruping, notwithstanding this immenss 
parasitic mass, just as freely as those not infested. 
Then consider the condition of the hog. We frequently find, 
in his | ver, a vesicle filled with fluid, apparently possessing no 
further *rganization. But examine it carefully, and we shall find 
within “ts enveloping tunic others, the rudiments of successive 
cells, i) various stages of growth. These are all young hydatids, 
whick contain still others, which increase in size until the parent 
sac is o distended that it finally bursts, and thus liberates a mul- 
titud of parasites, which, in their turn, undergo the same evolu- 
tion, '»ecoming each a parent hydatid, producing a subsequent 
genc’ ition, which diffuse themselves over the whole body of the 
pig; and hence arises that peculiar feature in pork known as 
meer ‘es. 
Examine the same animal after he is slaughtered, and you may 
possibly find in the intestines a large number of the ascaris lum- 
bricoides (the common worm of the human intestines); and they 
are so prolific that naturalists have calculated sixty-four millions 
of ova within the body of a single female, which are, at the proper 
season, deposited within the intestinal tube of the pig, who, not- 
withstanding, grows fat, and furnishes a savory meal for the lovers 
of pork. Sheep, also, are infested with a species of entozoa termed 
the “fluke,” besides other different species; and it is only when 
the latter become very numerous that they can be considered in- 
jurious. 
We might go on to show that every living being is more m 
less infested with parasites, and that purasites are, in their turn, 
the local habitation for other parasites. The very atmosphere we 
breathe, and which is the purificator of the vital current (the 
blood), teems -vith an innumerable host of living organized crea- 
tures. The water which serves to quench the thirst, that plays 
so important a part in our economy, and in the arts and sciences, 
whether it be the ocean, lake, river, pond, or gully, all contains 
crowds of parasites, or animalcule, at times, so numerous that 
several hundred thousand have, by means of a magnifying lens, 
been discovered in a single drop of this fluid. Yet such is good 
and pleasant to the taste; and the water is not injured thereby; 
neither is it, in turn, injurious to man. Dr. Lerpy states that he 
