Report on the progress of human anatomy and physiology in the year 1844-5 / [Sir James Paget].

  • James Paget
Date:
1846
Catalogue details

Licence: Public Domain Mark

Credit: Report on the progress of human anatomy and physiology in the year 1844-5 / [Sir James Paget]. Source: Wellcome Collection.

    57/64 (page 57)
    other radiating, for its dilatation,—but, also, that these movements are under the influence of two sets of nervous fibres, of which one set, distributed to the circular muscle, are derived from the third nerve through the ophthalmic ganglion, and the other, distributed to the radiating fibres, are supplied by the branches of the cervical spinal nerves which pass through the superior cervical ganglion of the sympathetic. The experiments show, as Valentin’s did, that after division of the third nerve the pupil dilates, and that after removal of the superior cervical ganglion it contracts. In animals killed by strychnine the pupil is dilated; but if, before giving the strychnine, one of the superior cervical ganglia be removed, and the pupil of the same side be thus made to contract, it dilates only a little after the administration of the strychnine, while, in the same case, the pupil of the opposite side is extremely dilated. Again, if one of the third nerves or the ophthalmic ganglion be irritated in a body still irritable, the pupil of the corre¬ sponding eye contracts slowly and does not dilate again. But if, after the pupil of a live animal has contracted on irritating the third nerve, the superior cervical ganglion be irritated, the pupil dilates again. But while these movements of the iris after death and on the irritation of its nerves indicate its muscular structure, Guarini relates another experiment to show that the turgescence of its vessels has also some share in producing or maintaining the contraction of the pupil Thus, he says that the contraction of the pupil, when after death the third nerve is irritated, is never so complete as it is during life ; because the circulation having ceased, the congestion of the blood¬ vessels with which the muscular fibres are interlaced, and which they compress when they contract, cannot take place; but the dilatation of the pupil on irritating the superior cervical ganglion after death is as complete as during life. Membrana Pigmenti. C. Bruch* describes the numerous round or oval nuclei among the pigment-cells scraped from the choroid, as forming a separate layer between the choroid and the cells of the pigment. Among those taken from the pig’s eye, he found many fixed in a delicate, pellucid, structureless membrane ; the}' lie, commonly, in close-set rowrs, or, more rarely, scattered in the membrane; and some, which have probably been accidentally separated, are found unattached. Bruch has traced this membrane in many animals, and in man, in whom it extends over the whole choroid, the ciliary ligament, and the posterior surface of the iris. Its nature and purpose are uncertain; whether it be only such a basement or germinal membrane as lies beneath the epithelium of mucous membrane in general, or a layer of embryo pigment-cells with cytoblastema, cannot be deter¬ mined ; but, if any part does, this deserves the name of membrana pigmenti. Tapetum. Ernst. Briickef has added observations to those which he published last year, to prove that the office of the tapetum is to reflect light, on the staff- shaped bodies of that part of the retina which is most used in vision, and so to make vision possible to certain animals, at times when those without a tapetum are in darkness. He has produced an extensive comparative anatomy of the tapetum ; and has shown that while all the other various colours which the tape¬ tum of the dog and other animals presents in different lights depend on it alone, the red colour which it occasionally reflects is due to the large vessels beneath it coming into view. And he has discovered that there are in different animals two distinct kinds of tapetum,—the one fibrous, the other cellular. The fibrous tapetum, which has been long known to consist of smooth, transparent, uudulat- ing fibres, is found in ruminants, solidungula, the elephant, some marsupials, and the whale tribe. The cellular tapetum, hitherto unknown, is found in the carnivora and in seals. The cells, which may be best seen after pieces of tape¬ tum have been macerated for a day or tw7o in w'ater with some hydrochloric acid or alcohol, are smooth, nucleated, elongated, unequally and imperfectly hexa¬ gonal, and very large, measuring from ’0008 to *0028 of an inch in diameter. * Untersuch. zur Kennt. des kdrnigen Pigments der Wirbeltliiere; Zurich, 1844, 4to, p. 6.