Whether an animal has or has not blood,
it cannot possibly be without this. In the Cephalopoda this part
consists of a fluid substance contained in a membrane, through which
runs the gullet on its way to the stomach. It is attached to the
body rather towards its dorsal surface, and by some is called the
mytis. Just such another organ is found also in the Crustacea and
there too is known by the same name. This part is at once fluid and
corporeal and, as before said, is traversed by the gullet. For had the
gullet been placed between the mytis and the dorsal surface of the
animal, the hardness of the back would have interfered with its due
dilatation in the act of deglutition. On the outer surface of the
mytis runs the intestine; and in contact with this latter is placed
the ink-bag, so that it may be removed as far as possible from the
mouth and its obnoxious fluid be kept at a distance from the nobler
and sovereign part. The position of the mytis shows that it
corresponds to the heart of sanguineous animals; for it occupies the
self-same place. The same is shown by the sweetness of its fluid,
which has the character of concocted matter and resembles blood.
In the Testacea the presiding seat of sensation is in a
corresponding position, but is less easily made out. It should,
however, always be looked for in some midway position; namely, in such
Testacea as are stationary, midway between the part by which food is
taken in and the channel through which either the excrement or the
spermatic fluid is voided, and, in those species which are capable
of locomotion, invariably midway between the right and left sides.
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