On Certain Cystic Worms, &c. By G. M. Giles. 
291 
confuse the condition with true tubercular infection, to numbers so 
enormous that the tubercles are rather too closely packed to be typical 
of the condition they mimic. In one instance so enormous were the 
numbers, that, putting aside such embryos as had developed suffi- 
ciently to simulate the macroscopic appearances of tubercle, others, 
which had too recently arrived to set up the protective proliferation 
that forms the tubercle, were so numerous that hardly a section could 
be found which did not exhibit two or three of them : this though 
the sections were of but small area. 
No helminthological fact can be more striking to the student of 
human pathology than the kindly way in which herbivorous animals 
tolerate the invasion of their solid viscera by cestode embryos. 
Large cysts, which would cause serious, if not fatal illness in the 
human subject, seem to cause little or no inconvenience to ruminant 
hosts. The walls of the protective cysts seem to be, one might almost 
say, instances of physiological proliferation rather than of inflamma- 
tory action, and there is commonly nothing whatever to show that the 
health of the animal has been in any way affected. This is especially 
the case with the liver. In the lungs, a more or less distinct zone of 
redness surrounds each tubercle ; and where they are numerous, a 
sort of verminous pneumonia may be set up, but even here any free 
spaces that may be left uninvaded appear but little altered. 
The nematode tubercles were found in the livers of mules which 
were destroyed owing to their being reduced to a hopeless condition 
by enormous numbers of Sclerostomum tetracanthum , free, and en- 
cysted in the intestinal submucosa. It is only quite lately that a 
renewed examination of the material I collected more than two years 
ago has eslablished their nematode origin. At the time I first 
observed them, I believed them to be cestode tubercles identical 
with those with which I was already familiar in cattle. In spite of 
the essential difference in the species originating the two sorts of 
helminth tubercle, it will, I think, be better to take their description 
together, as their resemblances or differences may thus be more 
easily emphasized with fewer repetitions than would be otherwise 
possible. 
In either case these helminth tubercles are, as I read the appear- 
ances, produced by the lodgment in a minute vessel of an embryo, 
which, being too large to pass, obstructs the vessel. 
The cestode embryos at first grow rapidly, and soon dilate their 
vascular sheath so as to alter it out of all recognizability. 
The nematode embryos do not appear to grow at all in their 
new lodgment, but their presence, equally with that of the cestode 
embryos, sets up a proliferation of the tissues of the vascular wall, 
and perhaps also of the cellular elements of the contained clot. In 
their case, however, the vascular wall remains— altered, it is true, but 
still recognizable, and from this difference in their behaviour to their 
surroundings there results a difference in their appearance which, 
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