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)