The Rot in Sheep. 
99 
dark bile while others are empty, which gives to the creature a 
peculiar parti-coloured hue. 
External Surface. — When the external surface is examined 
with a low magnifying power, the skin is found to be thickly 
covered with minute papilla; which point towards the posterior 
part of the body. (Seeji(/. 8.) In some specimens we have found 
only the anterior half of the creature thus covered, while in others 
no papilla; could be detected on any portion of the skin. These 
differences do not seem to mark any distinction of species, nor to 
be indicative of the age of the entozoon ; but are probably owing 
to a casting off or shedding of the papilla?, as we see in so many 
other creatures. The epidermic portion of the skin is very thin 
and transparent, and appears to be homogeneous. It is best ex- 
amined by stripping off a portion of the integument as a whole, 
when torn fragments of epidermis will be met with on the edges 
of the detached piece. The substance of the dermis or true skin 
appears to be composed of minute granules, arranged in some 
parts in a linear form both longitudinal and transverse, incor- 
porated with numerous cellules. 
Several of these peculiarities are very well depicted in Jiff. 3, on 
the preceding page, which represents a magnified view of the ex- 
ternal surface of the entozoon. In addition to the papillated skin, 
the mouth or anterior sucker (a), the ventral or posterior sucker (b), 
and the so-called intromittent organ or penis (c), are represented. 
Muscular System. — Immediately beneath the integument lies 
the muscular or contractile tissue, on which the various motions 
of the entozoon depend. In an animal the parenchyma of 
whose body is so pulpy as that of the distoma, it is almost im- 
possible clearly to demonstrate the arrangement of the muscular 
fibres. It seems, however, that most of them run in a longitudinal 
direction and others transversely, while some would appear to 
cross these at angles more or less acute. Towards the mouth 
the fibres are stronger and more clearly developed, as they also 
are about the region of the ventral sucker, their special arrange- 
ments, however, in regard to these organs will be hereafter 
considered. 
Aquiferous System. — Traversing the parenchymatous and other 
structures in every possible direction, immediately beneath the 
integument, are numerous tubes, exceedingly small in size, form- 
ing a beautiful rete, akin, as is supposed, to the capillary system 
of the higher order of animals. These tubes have been de- 
scribed as ending in minute ca;ca, and which they would appear 
here and there to do ; but their continuous connection and 
reticulated arrangement are well seen in flukes rendered trans- 
parent by immersion in glycerine. They give passage to a 
