The Lens and its Capsule

Speaking anatomically, the lenticular opacities, i.e., cataracts, are different according to whether the nucleus or the cortex is involved. There is a difference between the nucleus and the cortical substance….


THE crystalline lens, or crystalline body, is a doubly convex transparent solid body, with a rounded circumference; it is inclosed in a capsule, is situated behind the pupil, and in front of the vitreous body.

In Bowman’s words, the capsule of the lens, a transparent glass-like membrane closely surrounding the contained body, is hard and brittle, especially in front, but very elastic and permeable to fluid. The anterior surface is in contact with the iris towards the pupil, and recedes from it slightly at the circumference; the posterior rests closely on the vitreous body. Around the circumference is a space, called the Canal of Petit. The fore part of the capsule is several times thicker than the back, as far out as 1/16 of an inch from the circumference, where the suspensory ligament joins it; but beyond that spot it becomes thinner, and it is thinnest behind. In its nature the capsule of the lens resembles the glassy membrane at the back of the cornea, for it is structureless, and remains transparent under the action of acids, alcohol, and boiling water, and when ruptured, the edges roll up with the outer surface innermost.

By “structureless” is meant that our strongest magnifying powers are unable to show any further differentiation. It is very tough and exceedingly elastic.

The histology of the lens is admirably given in Stricker’s Manual of Human and Comparative Histology, vol. iii., which is translated by Dr. Power for the New Sydenham Society (London, 1873).

It is the work of Professor Babuchin, who was ably assisted by Sernoff. But it is much too elaborate for the present purpose.

Max Tetzer’s Compendium der Augenheilkunde, Gruenfeld’s third edition, Vienna, 1878,-by the way the best Manual of Ophthalmology extant,-is a mine from which we shall dig a little. Poor Tetzer was the most genial clinical instructor of his day (alas! so short), and made almost every student feel that he would go in for the eye. He puts the anatomy and histology of the lens thus tersely: The lens, with its posterior surface, fits into the plate-like groove of the vitreous. The connection of the posterior part of the capsule in this groove, is however, very loose, so that the capsule can be readily taken out. Of the greatest importance is the layer of the intracapsular cells, that are very pretty epithelial cells, like mosaic. This epithelium of the capsule, lying on its inner surface, is to be regarded as the matrix of the fibres of the lens. Particularly those cells towards the periphery give rise to the formation of the fibres of the lens.

The lens substance has a peculiar shape; its anterior surface is flatter, the posterior surface more convex. The proportion in the convexity is as ten to six. In the lens we distinguish the nucleus and the cortical substance. The cortical substance is rather softer, somewhat succulent; the nucleus, on the other hand, is a compact mass. The cortical substance can be divided into leaves (laminae), but the nucleus cannot be divided into leaves. Towards the equator the cortical substance is most considerable. This depends upon the development of the lens, because the peripheral layers are the youngest, while those layers that surround the nucleus are the oldest. The color of the lens in young individuals is as clear as water; the older the person the more it becomes metamorphosed, turning yellow, yellow- brown, even rusty-brown.

Structure of the Lens Substance.

The fibres of the lens are its most important constituent; they are six-sided prisms, so that on section of a lenticular fibre we get a hexagon. One fibre fits accurately to the other. The ends of the fibres are jagged like a saw, whereby the connection is more intimate. The fibres consist of a membrane, a contained fluid, in which globulin or crystalline was discovered, and of a nucleus, which, however, exists only in the young; in the older it has already disappeared.

The complicated arrangement of the fibres themselves will not here come under consideration.

The consistence of the fibres of the lens varies in accordance with the layer in which they are found. The superficial fibres are very soft and delicate, and the nearer the centre the more hard and resistant.

Nutrition of the Lens.

The lens has no blood-vessels. With regard to the nutrition of the lens, we consider the capsule as the matrix of the lens. On the inner surface of the capsule there is a layer of epithelial cells, so that here the further nutrition is carried on through cells. The capsule is as it were, the basement membrane for the epithelial cells; these grow and differentiate into lens fibres. Hence the lens proper is the product or fruit of the capsule, and it is this idea that we have found to encourage us in our therapeutical endeavors, more especially when considered in relation with its origin. The nutrition may reach the lens by transudation through the capsule.

Chemistry of the Lens.

The principal chemical constituents are of an albuminous nature; consisting, in fact, chiefly of globulin with a certain quantity of albuminate of potash and ordinary seralbumen. Other materials that have been ascertained to enter into the composition of the lens fibres are-a little fat, with traces of cholesterin, about one-half per cent of ashes, and sixty per cent of water. The qualitative characters, no doubt, vary with the layer from which the fibres are taken; for, apart from the fact that the central fibres are more resistant, the nucleus of the lens becomes much harder than the superficial layers under the same reagents; so that, in fishes, for example, the nucleus remains transparent, hard, and difficult to cut. The cloudiness of the fibres of the lens, and the formation of vacuolae in their interior, are occasioned by the action of reagents which withdraw water from them.

Probably this explains the modus operandi of salt, sugar, alcohol, and secondarily, of ergot in the artificial production of cataract.

Embryology of the Lens and its Capsule.

The development of the crystalline and its coat must, of course, be considered in connection with that of the eye as a whole. Now the eyes begin to be developed at a very early period, in the form of two hollow processes projecting one from each side of the first primary cerebral vesicle. Each process becomes converted into a flask-shaped vesicle, called the primary optic vesicle, which communicates by a hollow pedicle with the base of the posterior division of the first primary cerebral vesicle. According to the observations of Remak on the chick, the pedicles, originally separate, come together, and their cavities temporarily communicate,-a condition which may explain the formation of the optic commissure.

The primary optic vesicle comes into contact at its extremity with the CUTICLE, which somewhat later becomes invaginated at this point, and forms a small pouch pressing inwards on the optic vesicle; the aperture of this pouch becomes constricted and closed, and the pouch is soon converted into a shut sac, within which the contents, subsequently becoming solid form the lens and its capsule. After the lens has been thus separated from the CUTICLE the deeper tissue contributes to the formation of the secondary optic vesicle. This is as much of the embryonic development of the eye as we need for the present purpose; from it we see that the lens and its capsule are differentiated skin. This should be well remembered.

The investigations of Babuchin and of Sernoff lead them to differ but slightly from this in their conclusions. They say that, as regards the origin of the lens and the mode of development of its fibres, it is obvious from the direct transition of the anterior epithelial layer of the lens into the posterior fibrous layer, that each fibre of the lens is simply a colossal and greatly elongated epithelial cell, and the history of development shows further that the persistent portions of the body of the lens arise from the EPIDERMOID external layer of the embryo.

The question of the development of the capsule is still open, according to Sernoff, who has long been occupied with its investigation; in the meantime he would appear to deny both its epidermoid origin, and also that it is the product of the excretion of the epithelial cells and of the fibres of the lens. Babuchin inclines to classify it with the metamorphosed connective tissue formation.

But some light may be thrown on the question of the origin of the capsule of the lens-a very important question, by the way, for gaining a little firm ground for our therapeutic endeavors-by comparing it with the membrane of Descemet.

The capsule of the lens and the membrane of Descemet have many properties in common; thus portions of either, when treated with reagents (as, for instance, permanganate of potash, or a ten per cent. solution of common salt) will roll inwards like paper that has been long rolled up, and they are both glass-like or hyaline. Hence the opinion of Babuchin, that the capsule of the lens is transparent connective tissue, would seem very probable. According to Rollett, the histogenesis of the cornea requires to be again worked over, especially with the aid of the silver and gold methods of preparation. But, leaving for the present the origin of the capsule undecided, we are in no doubt of the EPIDERMOID nature of the lens, and also in no doubt of the endothelial nature of the intercapsular cells.

James Compton Burnett
James Compton Burnett was born on July 10, 1840 and died April 2, 1901. Dr. Burnett attended medical school in Vienna, Austria in 1865. Alfred Hawkes converted him to homeopathy in 1872 (in Glasgow). In 1876 he took his MD degree.
Burnett was one of the first to speak about vaccination triggering illness. This was discussed in his book, Vaccinosis, published in 1884. He introduced the remedy Bacillinum. He authored twenty books, including the much loved "Fifty Reason for Being a Homeopath." He was the editor of The Homoeopathic World.