Explanation of Pkate XI, figs. 1-3:

'Fig. 1. A portion of the transverse section of an ox's rib. Shewing the effect of a slight digestion by trypsin. Bone hardened in chromic acid and -decalcified by the careful addition of nitric acid. p. Periosteum. pl. That part of shaft wall mainly occupied by periosteal lamellse; the structures are intact beyond the sharper definition of the contour lines where a removal of the cement has occurred. i. Inner part of shaft, in which the effect of the digestion is most marked, The Haversian systems and internal masses of lamellse as also those of the cancellous tissue are intact. a. Gap where the intermediate lamellie are gone. b. Channel for blood-vessel in these lamellae.

Fig. 2. Periosteal lamellae from ox's rib after brief digestion. Bone treated same as that in fig. 1. l. A lamina in longitudinal section. t. One in transverse section. s. Space for lacuna. The outlines of lacunae and canaliculi are omitted.

Fig. 3. Part of a Haversian system. The matrix has become homogoneous and transparent. a. Membrane indicating former limi of the Haversian canal. b. Later membrane lining permanent channel.' (383)

Fig. 1 in text:

'there were to be seen disturbances in the arraigement of the intermediate lamellae in the inner part of the shaft; these presented a confused mass near the inner surface, and in some places were entirely wanting, there being gaps in the section (P1. XI. Fig. 1). The Haversian systems stood intact amidst the debris, as did also the masses of lamellae forming the inner surface of the shaft and cancellous tissue.' (372-373) 

Fig. 2 in text:

In Schäfer's characterization, ''two sets of fibres constituting the lamella are held to be separable from their neighbours along an ideal plane any point of which is indicated by the occurrence of a lacuna' [note: 'A similar opinion is held by Klein. Atlas of Histology. Pt. iv., PI. xII. fig. 2, and p. 55.']

This arrangement is not supported by an examination of the structures in question, for lacunae are found in the thickness and course of one set of fibres, in support of which there are the statements already quoted of v. Ebner (l.c. [' Sitzb. der math. Naturwiss. kais. Acad. der Wiss. Wien, Bd. LXI., Abth. II. 1876.'] p. 70), and his drawings especially Taf. I. Fig. 4, and Taf. III. Fig. 25. b.  [note: 'Ranvier. Trait technique d'Histologie, 1875, p. 314, fig. 101.']. Ranvier [note: 'Ranvier. Trait technique d'Histologie, 1875, p. 314, fig. 101.'] gives drawings unconsciously supporting this view. My own observations have convinced me of the almost constant nature of the fact. Pl. XI. fig. 2.' (365-366)

'Alternate lamellas are similar to each other, and such a view is represented in Fig. 2 (Pl. XI.). One set has the appearance of continuous bands, whilst the other consists of small masses in single rows, separated by bridges that seem to join the band-like set. Both are lamellk of the same constitution, only they are seen in different section.' (366)

'I would maintain that the lamella consists of one set of fibres having a parallel arrangement and that these fibres send bundles of fibrils to one another occasionally, as has been shewn by v. Ebner. The position occupied by the lacunae is one which has a more definite relation to one set of fibres than to two, as specially indicated by their occurrence in the thickness of one set of fibres (Fig. 2, s).' (367)

'Either two sets of fibres are empirically and unnecessarily to be assigned to a lamella, or the more natural division is to be followed of accepting one set of fibres having a common direction, and lying in the same plane, of greater or less extent, as constituting a bone lamella.

In conclusion I would here allude to Fig. 2, which is a sketch of a number of subperiosteal lamellae from the rib of an adult ox. The sketch was made before this particular relation of the lacuna, to the lamellwe was in my mind, and has remained unaltered since.

The alternate layers of bands and masses are lamellee seen in different section. Three lacunae are visible; the two on the right hand are situated in lamellae which have different directions, the upper one being in a situation corresponding to that shewn at s, but not so marked, whilst the lower one lies in a thin longitudinally-cut lamella.' (368)

'In the subperiosteal and intermediate lamelle the fusion into each other of similarly directed lamellke is more frequent than in the Haversian systems. This is well shewn in Fig. 2.' (369)

'Examination with a power of 300 diam. shewed the lamellar structure very plainly in the coherent parts, the alternating arrangement in the matrix of bands and rows of bodies being more distinct than before digestion and very sharply defined...

The appearance was so distinct that there could be no doubt as to the construction to be put upon the observed arrangement. Where the band and dot series were most markedly seen, that is where the plane of section had followed the course of one set of fibres, these alternating layers of bands exhibiting longitudinal fibrillation, and others composed of little blocks separated from each other by almost empty spaces occurred; the blocks exhibited a granular appearance, the sectional view of the fibrils composing the bundles to whose cut extremities the appearance of blocks is due (Fig. 2).

Particularly well seen, in the same locality, were the frequent junctions or fusions which lamellae of a similar direction undergo with each other:... Gentle curves may and no doubt do occutr in the fibres of lamellie, insufficient in themselves however to alter the relation of parts. In Fig. 2 are represented a number of such lamelle, of periosteal formation, these being especially chosen on account of the behaviour of the lamellie and the little regularity of arrangement which obtains in them. (373-374)

'In the figure the lacunar outlines have been omitted; the spaces occupied by them are indicated by the occurrence around them of the bundles of fibrillae; the canaliculi are also omitted. These spaces are in every case, of the three represented in the figure, in the thickness of a lamella, the most marked being at $ (Fig. 2);' (374)

'A point particularly noticeable is the difference in the thickness of the lamelle; the great irregularity seen here (Fig. 2) is one which appertains to the periosteal lamellaw, those of the Haversian systems being much more regular, a fact which has already been alluded to.' (374)

Fig. 3 in text:

'In some systems membranes similar to that lining the canal were found further in the matrix towards the periphery, sometimes at no very great distance from the central canal. Such a membrane is shewn in (PI. XI.) Fig. 3, where b is the internal, and a the outer one, situated in the substance of the matrix.' (379) 

Explanation of figs. on Plate XIII:

Fig. 1. V. S. cornea of albino rabbit, hardened in a mixture of chromic acid aind spirit; a, corneal epithelium; b, cornea proper; c, elastic lamina, posterior epithelium removed; d, clear hem on corneal epithelium.

Fig. 2. a, various forms of cells from lowest layer of columnar epithelium isolated by iodised serum; b, similar cells; c, bases of a and b; d, 'digitate' cells from higher layer; e, prickle cells further up towards surface of cornea.

Fig. 3. Peculiar appearance sometimes seen in vertical sections of cornea of ox; a, tall compressed cells; b, similar cells swollen out and compressing a.

Fig. 4. Corneal epithelial cells of ox isolated by iodised serum; a and b, lowest layer of cells; b. apex grasped by fangs of a digitate cell; c, ' digitate' cells; d, smaller digoitate cells higher up; e, prickle cells.' (338)

Fig. 1 in text:

'On examining a vertical section of a cornea which h, as been stained with picro-carmine and mounted in glycerine, we get such a view as is shown in Fig. 1, Pl. XIII., where a represents the epithelium covering the anterior surface of the cornea proper, b; c the posterior elastic lamina. The picro-carmine has stained the nuclei of all the cells red, their substance yellow, and the cornea proper and elastic lamina red.' (335)

'Fig. 1 d is very instructive, for it shows a part of the corneal epithelium detached from the cornea proper, each cell showing its clear hem.' (336)

Fig. 2 in text:

'The columnar cells forming the lowest layer are not all of the same height, nor of the same size, as generally represented. This is well brought out in Fig. 2, a and b, and Fig. 2 c shows the bases of these cells, and here we note that they are not all of the same size at the base...

The lowest columnar cells are always slightly expanded at their bases, and the clear band is not so marked as after hardening. Their appearance is shown in Fig. 2 a, taken from a preparation isolated by iodised serum. From the middle layers a few prickle cells are always obtained of various forms, and Fig. 2 b shows the difference in the height of these cells. From above this layer we have succeeded in isolating smaller cells-digitate cells, whose teeth fit in between and grasp the apices of several columnar cells. We shall allude to these more fully presently. Prickle cells can also be easily isolated, Fig. 2 e.' (336)

Fig. 3 in text:

'Fig. 3 gives a view of a section of the cornea of the ox... but certain of the appearances however are peculiar and apt to lead one into error, unless controlled by examining other preparations. Every here and there groups of short broad cells (b) are to be observed, occurring between groups of tall cells (a). This is not a normal appearance but due to the swelling out of those at b compressing those at a, and thus giving rise to this peculiar appearance, which we have also seen in the rabbit's cornea.' (337)

Fig. 4 in text:

'We find that Rollett [note: 'Rollett, article Cornea in Stricker's Histology, English Edition, p. 424.'] has also noticed in the lowest layer of cells of the cornea of some animals a basal 'hem' or 'border'... He says, "The expanded basal borders of the cells are so applied to each other, or are so superimposed upon one another by their thin edges, that the borders of the several cells seen collectively in situ make a bright stria which forms the line of demarcation between the epithelium and the corneal tissuet." [note: 'L.c. p. 427.'] This is also the view we take of the matter, for the base of each cell is always expanded somewhat and broader than the part immediately above the base (Fig. 4, a and b).

We now proceeded to isolate the cells from the cornea of the ox by means of iodized serum. Fig. 4, a and b, shows the lowest layer of columnar cells. They are very remarkable on account of their being so elongated; they are as elongated as any epithelium in the body .Invariably their base is flat as described by Prof. Cleland [note: 'On the Epithelium of the Cornea of the Ox, Journal of Anat. and Physiology, Vol. II. P. 362.']... The clear hem is very delicate and not nearly so pronounced as in the rabbit. Above these cells Prof. Cleland in 1867 described cells of peculiar shape, to which he gave the name 'digitate'. "They are of irregular shape, about twice as broad as the columnar epithelium, but by no means so elongated." He describes them as " rounded and even in outline at the superficial extremity," (but they are not all so (Fig. 4 c), though some are,) and "jagged at the other, and send in processes or 'digitations', which may be three or four in number, and which appear to fit in between the tapering points of the columnar cells." We have directed especial attention to these peculiar 'digitate' cells, for their existence has been denied by Rollett [note: 'Op. c. p. 424'], but there cannot be the slightest doubt of their existence... They present much the appearance of a molar tooth with its fangs, dipping in between the apices of the columnar cells, and Fig. 4 b shows how they are placed, each cell being in relation with the apices of several columnar cells.' (337-338)

'Above this layer of digitate cells we have a stratum of smaller cells some of which are 'digitate' (Fig. 4 d), and there is a gradual transition between them and small prickle cells (which occur in very large numbers in the cornea of the ox and sheep), and gradually as we pass upwards we come to the large flat squames on the surface.' (338)