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96 O B S E R V A T I O N S ON THE
But in fome cafes of hydrocephalus intemus, m which the retina feemed
to have very little fenfibility, I have feen the pupil remarkably dilated when
the eye was expofed to a bright light, and, when the light was removed,
it was fenfibly leflencd *.
When a perfon examines an objea brought near to the eye, the pupil is
contraaed, although the objeft be of a black colour, fo as not to affeS the
eye by an increafe of light. With this obfervation let us conned another,
to wit, that, when a fmall printed book is brought fo near the eye, that its
letters begin to feem confufed and intermixed, if we interpofe a card, with
a very fmall hole in it, the letters are again feen diftinilly.
In one fpeeies of bird, the parrot, I long ago remavked, that the pupil
was afFefted by the paffions of the mind of the animal, independent of
the light upon the eye,
2. When a found is made fuddenly, not only the external ears of a quadruped
are moved, but it has been, with great probability, fuppofed, that
the internal mufcles of the ear ad at the fame time.
3. If the nofe is violently irritated, we fneeze; if the throat or ftomach,
we vomit; if the inner membrane of the lungs, we cough; if the redtum
or gravid uterus, the containing parts of the abdomen contraft ftrongly
and readily. Every one of thcfe adtions is complex, yet regular.
4. The motion of the blood in the lungs, and a proper change of air, are
promoted by ordinary refpiration. But, according to the quality or quantity
of the blood or air within the lungs, we may obferve the manner of
refpiration varied.
5- By
• Khowedthis, in one cafe, to Dr N. Spens in 1770) and in another, very lately, to Dr D. Rutherford.
N E R V O U S S Y S T E M . 97
5. By the irritation of the external organs of generation, the difcharge of
the femen is made in the male ; and, in the female, the uterine tubes lay
hold of the ovaria.
6. When the bladder of urine is to be emptied, a prelTure is firft made
upon it by the contraction of the diaphragm and abdominal mufcles ; afterwax'ds,
by the Heady and uniform contradion of its own mufcular coat,
the urine is propelled.
7. When wholefome food is received into the ftomach and inteflinal tube,
thefe perform elegant and complex motions, called periftaltic and antiperiftaltic.
8. If, inftead of ordinary food, a hurtful fubftance is taken into the ftomach,
the antiperiftaltic motion gets the better of the periftaltic, and
comes to be affifted by the diftant mufcles, which are fo fituated as to be
able to comprefs the ftomach, or the perfon vomits. But, when the hurtful
matter is within the colon, or re£lum, whether it has defcended from
above, or been injeéted from below, the periftaltic motion is gi-eatly increafed,
and the fubftance is difcharged downwni-ds.
In the pécora, for inftance, in the cow, we find not only a complex
ftruñure and aâion of the four ftomachs, but that aftion will be found to
be varied according to the kind of food, or the changes it has undergone.
The cow fed on grafs ruminates, or chews the cud; but, in the calf, whilft
fed on milk, I have not obferved rumination ; yet, from the quantity of
milk the calf fucks, there can be no doubt that the firft ftomach ferves as a
receptacle for the milk. In the cow, then, the crude grafs palTes from the
mouth into the firft ftomach, and is afterwards, in ruminating, brought
back into the mouth, in order to be more thoroughly chewed. When
fwallowed a fécond time, it is conveyed into the fécond, and from it into
the third and fourth ftomachs. But the milk pafles from the firft ftomach
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