118 
MESSRS. J. TOMES AND C. DE MORGAN ON THE 
bones altogether destitute of circuinferential laminae, and very few with these laminae 
complete ; while the encircling of several Haversian systems with laminae common to 
the whole is the exception rather than the rule. 
In the progress of their investigations the authors have failed to discover any 
instances in which pre-existing laminae, partially absorbed, have become continuous 
with newly-developed ones, end to end ; indeed there seems good reason for supposing 
that such seldom, if ever occurs, otherwise the Haversian systems would not be so 
strongly marked, neither should we have the festooned outline to the systems IHng 
against the cut ends of the laminae, in the manner shown in Plates VI. and VII. figs. 1 
and 10. 
In examining Haversian systems divided transversely, one will be occasionalH 
found in which the canal has been completely obliterated by the development of a 
lacunal cell in its centre. This condition is illustrated in fig. 1 c. 
Ossified Cartilage of Joints. — Dr. Sharpey has shown that beneath the articular 
cartilage lies a layer of bone produced by the gradual ossification of this tissue"*. 
Professor K.6lliker'|~ has observed this form of bone to be present in all the aiticu- 
lations, excepting that of the jaw and the hyoid bone, in which situations he has failed 
to detect it. The authors have numerous sections from the articular process of the 
lower jaw, in all of which it is present, and although in smaller amount than is usually 
found in corresponding parts of other bones, still it is sufficiently distinct. The pecu- 
liarity of the articular bone consists in the maintenance of the same arrangement of 
parts as existed in the cartilage prior to its conversion into bone. The cells for the 
most part are arranged in groups or in lines parallel with the long axis of the bone, 
each cell presenting a roundish mass surrounded by granules, and rendered rather 
indefinite in outline. Not uncommonly several cells become connected end to end, 
thus producing an elongated form. It is when in this condition that the cells and 
basement tissue may be restored to the appearance of cartilage by the use of hydro- 
chloric acid. Occasionally, however, a cell becomes converted into a well-developed 
lacuna, and near the ordinary bone the cells may be seen in more or less advanced 
stages towards their conversion (Plate VII. fig. 17). 
In the ossified cartilage, when the tissue attains a considerable thickness, broad and 
ill-defined lines or bands of opacity may generally be found running parallel with the 
articular surface, and giving a stratified character to the part in which they are 
situated, as shown in fig. \7 b. When seen by transmitted light, these lines appear of 
* Dr. Quain’s Anatomy, fifth edition, by Mr. Quain and Dr. Sharpey, part ii. page 15S. “ In the slow 
growth of bone w'hich encroaches on the attached surface of articular cartilage, the ossification would almost 
seem to be produced merely by the impregnation of the cartilaginous matrix with earthy matter (correspond- 
ing with the first step of the ordinary process) ; and in this case, the cells and clusters of cells being surrounded 
by calcified matrix, may remain as little vacuities or lacunae in the bone ; but this as well as the formation of 
lacunae in the crusta petrosa of the teeth, and the production of adventitious bony deposits in different textures, 
requires further investigation.” 
t Kolliker, page 318, oper. cit. 
