An elementary compendium of physiology; for the use of students / By F. Magendie ; Translated from the French, with copious notes, tables and illustrations by E. Milligan.

  • Magendie, François, 1783-1855. Précis élémentaire de physiologie. English
Date:
1826
Catalogue details

Licence: Public Domain Mark

Credit: An elementary compendium of physiology; for the use of students / By F. Magendie ; Translated from the French, with copious notes, tables and illustrations by E. Milligan. Source: Wellcome Collection.

    80/668 (page 44)
    immovable and dilated; the same thing happens to cats and dogs, when we divide the fifth pair. Upon rabbits and guinea-pigs, on the contrary, the pupil contracts, in consequence of the division of that nerve. The section of these nerves ceasing, causes also the motions of the pupil to cease; and M. H. Mayo has ascertained, that upon birds, the division of the third pair produces also immo- hility of the same opening. Thus the motions of the iris are sub¬ ject to nervous influence; and if we call to mind the disposition of the fibres of that membrane, we cannot help regarding them as muscular movements, though they still differ in this, as we have seen, that they cannot be excited by direct irritation.* The ciliary nerves of man are derived from two sources; the most numerous series arises from the ganglion; the other directly from the nasal nerve. It is probable that the first preside over the dilatation, the second over the contractions of the iris; but nothing has hitherto fully established that pointi (Joicrn. Phys, iv.) Uses of the choroid membrane. Uses of the The choroid is of use to vision, principally by the dark mat- fhoroid, ^ , , . , * ^ ter with which it is impregnated, and which absorbs the light immediately after it has traversed the retina. One may consider, as a confirmation of this opinion, what ha])pens to some indivi¬ duals in whom some parts of this membrane become varicose ; the dilated vessels throw off the dark matter which covered them, and every time that the image of the object falls upon the point of the retina corresponding to these vessels, the object appears spotted with red. The state of vision in albino men and animals, in which the choroid and the iris are not coloured black, supports still more this assertion; vision is extremely imperfect in them : during the day, they can scarcely see sufficiently to go about. * Individuals weakened by venereal excesses, or labouring under tabes meseu- terica, worms, or hydroceplialus, have the pupil enlarged; narcotic plants, par¬ ticularly belladonna, applied for some hours on the conjunctiva, dilate the pupil; in cerebral allectious, it is sometimes contracted, sometimes dilated. Its motions, in general, indicate the state of sensibility in the retina. The consideration of thcscj and of its state, is peculiarly serviceable in medicine.