STRUCTURE AND DEVELOPMENT OF BONE. 
115 
arrested, when the formation of ordinary circumferential laminae is assumed in some 
cases to be again replaced by the development of undulating laminae. It must 
however be remembered that in the rapidly growing bone of young subjects lamina- 
tion is much less strongly pronounced than in the bones of the adult (Plate VI. fig. 4), 
and that in many cases it is indicated more distinctly by the arrangement of the 
lacunae than by the presence of well-marked outlines in the laminae themselves. 
In addition to laminated tissue we sometimes find portions of superficial bone run. 
in, as it were, between two or three Haversian systems, and without any appearance 
of lamination, but with a general transparency, and with lacunae scattered through it 
of indefinite form, and wanting in that arrangement which prevails in laminated 
bone*. 
Lacunae of Bone . — In a transverse section of the Haversian systems the lacunae are 
seen as elongated oval spaces, lying amongst, and with their long axes in the direc- 
tion of, the laminae ; numerous canaliculi proceed from them, the bulk of which in 
this view pass oflf towards either the Haversian canals or the outer surface of the 
systems. The lacunae are however somewhat different in appearance at different 
ages of the systems and of the subject. In youth they are large, numerous, and 
richly supplied with canaliculi ; on the other hand, in an old subject they are less 
numerous and have fewer canaliculi. Moreover, they vary a little in character in 
different parts of the same preparation, according to the age of the particular spot in 
which they are examined (Plate VI. fig. 6). Then, again, they frequently exist without 
canaliculi ; while in other cases they may be found, together with the canaliculi, in 
great part filled up with solid matter, leaving only a small round open space in their 
centre. This state of consolidation has not, so far as the authors are aware, been 
previously observed. It is however present to a considerable extent in the long 
bones of adults who have in infancy suffered from rickets, and whose bones have 
remained permanently distorted (Plate VII. fig. 12 a and h). More rarely a similar 
condition may be seen in the bones of those who have passed the middle period of 
life without having suffered from rickets in childhood. Hence consolidation must 
be regarded as a normal condition of the lacunae, of occasional occurrence, rather 
than as the result of disease. 
In favourable sections it may be shown that both the lacunae and canaliculi have 
parietes, which are manifested by appearances similar to those observed in the den- 
tinal tubes 'I'. In lacunae which have no canaliculi the walls are well-marked, and in 
* Kolliker, oper. cit. p. 288, objects to the opinion of Arnold that the interstitial laminse have a different 
origin from the external and internal circumferential laminse, the former of which he believes to originate in the 
cartilage, the latter in the external and internal periosteum. 
Kolliker’s views are inserted in the text, but it is seen above that the observations of the authors do not 
coincide with those of either Arnold or Kolliker. 
t This point will receive additional confirmation in a subsequent part of the paper, when the development 
of the lacimse and canaliculi is described. 
