Report on the progress of human anatomy and physiology in the year 1843-4 / [Sir James Paget].

  • James Paget
Date:
1845
Catalogue details

Licence: Public Domain Mark

Credit: Report on the progress of human anatomy and physiology in the year 1843-4 / [Sir James Paget]. Source: Wellcome Collection.

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    these muscles, and that in a recent case of accident he had an opportunity of ob¬ serving- their antagonist action. A man received a small penetrating wound through the lower part of the cornea, and a point just higher up in the iris. When the cornea healed, a triangular false pupil was found at the wound of the iris. Both this and the natural pupil could contract and dilate ; but, on the contact of light, the false pupil dilated and enlarged when the natural one contracted, and the false pupil contracted when, in the absence of light, the natural one was dilated. [The result of a number of observations in cases of artificial pupil, wounds of the iris, &c., by E. H. Weber,* went to prove, that the movements which occurred could not be explained by supposing that the iris has circular or radiated fibres, or both, but only by believing that its irritable part consists of fibres variously woven together without any definite direction.] A good discussion of this subject has been published by Dr. C. R. Hall.-j- He considers that the iris has a circular muscle for the contraction of the pupil; that the dilatation of the pupil depends, probably, on the cellular tissue or the blood¬ vessels of the iris having an unusual vital contractility; and that the only effect of the elasticity of the tissues of the iris is to accommodate it to changes of size, and to restore it from extremes to a medium state—i. e. to the size which it usually has after death. Valentinj has found, in two rabbits, that four months after the extraction of the lens, a new' body has been produced smaller than it, yet presenting, to microscopic examination, the peculiar ceils and fibres of the natural lens in stages of develop¬ ment similar to those through which they naturally pass. These were mixed however, with minute granules; their arrangement was not quite regular in all parts; and in both cases there W'as at the lower part of the new lens, opposite the injured part of the capsule, a yellow turbid portion formed of a finely granular substance quite different from lens substance. In both cases the capsule of the lens was transparent, without any trace of blood-vessels. The appearances indi¬ cated that the new lens was formed from cytoblastematous substance oozing into the emptied capsule, and that thus its harder central parts were those which had been longest engaged in development, and were most perfect. Ernst Briicke§ has pointed out an ingenious mode of demonstrating the structure of the vitreous humour, derived from the fact that when two solutions which will precipitate each other, permeate, or are imbibed in, membranous septa, the precipitate first forms in and upon the membrane. By placing the vitreous humour of an eye cut verti¬ cally and transversely behind the lens in a concentrated solution of acetate of lead he found its surface soon covered with a white substance, and when, some hours after, a portion was cut off' from the posterior part, the section was seen marked by fine milk-white streaks, which were edges of layers of which the outermost lay parallel to the retina, the innermost parallel to the posterior surface of the lens. The distances between the streaks were greatest in the axis of the eve, and became less towards the zonula, where they were about of an inch apart. ‘The margin of the layer appeared to be connected with the hyaloid membrane near the zonula, but in what way could not be determined. The vitreous bodies thus treated with lead separate more easily in the direction of the layers than in any other. Eyelids. Dr. Zeis|| has found that the eyelids of young animals born blind (and probably, also, those of the human fetus in utero,) are held together by a thin layer of gelatinous substance, which is interposed between their adjacent margins, and bleeds when torn across very soon after birth. Every day after birth this layer (displayed by vertical sections through the eyelids,) becomes thinner; at the same time, the fissure between the eyelids growsdeeper, making progress from before backwards, as if by the gradual eversion of the skin of their adjacent margins; and after the first day, vessels are not detected in the inter¬ mediate substance by either bleeding or minute injections. * Hildebrandt’s Anatomie, Bd. iv, p. 80. + Edinb. Med. and Surg. Journal, July 1844. t Oesterreichische medic. Woelienschrift, Fevr. 10, 1844; from Henle and Pfeuffer’s Zeitsrhrift 1843, Bd. i. Heft ii. § Muller's Archiv. 1843, Heft iv, p. 344. Pappenheim (Specielle Gewebelehre des Auges, 1842, p. 182,) said that the vitreous humour, when treated by carbonate of potass, “may be stripped in concentric layers almost like a bulb;” but did not demonstrate any of these layers of membrane. II V. Walther and V. Ammon’s Journal fur Chirurgie, Bd, ii, St. ii.