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.

    58/64 (page 58)
    With transmitted light they appear yellowish, and their nuclei pellucid ; but with reflected light, they are beautifully blue and their nuclei black. They are pecu¬ liarly subject to deposits of earthy matter. Retina. Pacini* has described the retina as consisting of five layers. The first or most internal is formed of the expansion of the white double-contoured (?) fibres of the optic nerve, lying close together in a transparent layer. The second is a single layer of nucleated and nucleolated transparent corpuscles, like simple ganglion-corpuscles, which he calls nerve-cells. The third, of a reddish-yellow colour, consists of gray nerve-fibres arranged in rays, which terminate in the cells of the second layer. The' fourth is composed of several layers of corpuscles, identical with those described by Ehrenberg in the cortical substance of the brain and in other parts of the nervous system, and called by Pacini, from their nuclear characters, nuclear nerve-corpuscles. The fifth layer is formed by the little cy- linders of the membrane of Jacob [the staff-shaped bodies of others]. Of these layers, the 1st, 4th, and 5th cease at the ciliary ligament ; but the 2d and the 3d, as if forming together a true ganglionic system, appear to be continued over the ciliary processes and iris. Lens. Sundry observations on the structure of the lens are published by Pro¬ fessor Harting.j- Among them are the following. In both the new-born child and the adult he finds some of its flat fibres composed of rows of cells fixed end to end ; and some having in or on their walls distinct round or oval nuclei, each with two or three very small irregular nucleoli. Both these kinds of fibres are found only at the equator of the lens, in which part they form the outermost layer. Neither the deeper layers at this part, nor the superficial layers near the poles, present a trace of such fibres. The lens of the new-born child has many more of the fibres with nuclei than that of the adult has. In the lens of a cow, just beneath the surface, and in that of a titmouse (Parus major), near its nucleus, he found some of the fibres composed of from five to seven finer parallel fibrils ; and in other fibres near the surface of the lens of the titmouse, there were transverse striae, which (like Wagner, who has also observed such fibres) he compares to those of the primitive fibres of muscle. Vitreous Humour. Ernst BriickeJ has confirmed the account wdiich he gave of the laminated structure of the vitreous humour by another mode of demonstra¬ tion. If an eye, frozen hard, be slowly thawed, and the sclerotica and other membranes be separated gently as soon as they are soft enough, lamellae of ice may be split off’ from the vitreous humour, exposing the layers of membrane of which it consists, the outer layers being parallel to the retina, the inner to the posterior surface of the lens; and all apparently structureless. A more exact account of the structure of the vitreous humour is rendered by Hannover.§ He has examined it principally and with most advantage in the eyes of horses, hardened in chromic acid, so that sections in various directions could be made through them. By these means he has cleared up a doubt which Briicke’s essay left, by finding that the several layers which compose the vitreous humour all form completely closed sacs, the outer sacs inclosing the inner, and all imitating the general form of the front of the eye behind the lens. Thus, in its laminated arrangement, the vitreous humour somewhat resembles a bulb, and the shape of its layers or sacs is such, that a line drawn from the middle of the optic nerve to the middle of the posterior wall of the lens would pass through the apices and the middles of the convex bases of them all. On this same plan of concentric sacs of delicate membrane are formed the vitreous humours of the cat, dog, ox, sheep, and horse. But the human vitreous * Atti della sesta Riunione degli Scienz. Italiani, in the Ann. Univ. di Medicina, Luglio, 1845. t Tijdschrift voor Natuurl. Geschied. en Physiol., 1845, d. xii, st. 1. His account of the growth of the lens is mentioned under the head of Nutrition. { Muller’s Archiv, 1845, Hefte ii, iii. For his former account, see the last Report, p. 57- § Ibid. 1845, Heft v. There is in the same journal a paper by him on the arrangement of the fibres of the lens; but his description could not be understood without diagrams.