STRUCTURE AND DEVELOPMENT OF BONE. 
113 
m such a system, there are more laminse on one side than on the other, and those on 
the side occupied by the greatest number are thicker in their centres than at their 
extremities, where they become gradually thinner, and are ultimately lost. The 
inner lamina, whether the systems are eccentric or not, forms, when the development 
is completed, a perfect ring, and not tinfreqaently presents a second peculiarity. The 
tissue of which it is composed is transparent, and affords, with our present means of 
investigation, little evidence of structure (Plate VI. figs. 6 and ’]). It is transparent 
and glass-like, resembling that tissue which lines the Haversian canals in the antlers 
of the Cervidee before they are cast (Plate VII. fig. 9). 
The interstitial laminse are abundant, and strongly marked in transverse sections 
of long bones, or in any sections of bone in which the Haversian systems are cut 
transversely. The laminse vary both as to their number and length, and are usually 
more or less curved. They are arranged throughout the bone in well-defined isolated 
groups,in each of which the constituent laminse are parallel (Plate VI. fig. 1 h). Professor 
Kolliker*, when treating of this subject, observes that it is difficult to account for the 
presence of the interstitial laminse, and suggests that the appearance may perhaps be 
produced by the Haversian systems being cut obliquely, but at the same time admits 
that this explanation is not satisfactory. M. Kolliker had not recognized the pre- 
sence of the Haversian spaces and the manner of their production and subsequent 
occupation, otherwise he would have seen that the interstitial laminse are the remain- 
ing parts of Haversian systems, the larger portions of which had been removed by 
absorption. But that the term interstitial laminae is already in use and has a definite 
meaning, the authors would have proposed the substitution of partial Haversian 
systems, as being more descriptive of these parts. 
In addition to the laminse of the perfect and imperfect Haversian systems, others 
that surround several linearly arranged systems are not uncommon, producing the 
appearance illustrated in Plate VI. fig. 5. In these instances a large oval system of 
laminse has become occupied by several lesser ones. The occurrence of one system 
within another is by no means rare. We may then see the characteristic emarginated 
outline of the older system, and within this a second similar outline marking the 
periphery of the younger system, as shown in Plate VI. fig. 6, in which the lamination 
of each is delineated -f-. 
The circumferential laminse are the most external, and where they exist form the 
surface of the bone. Their occurrence, however, is by no means so constant as is 
generally described, and even when present they seldom extend perfectly round the 
bone. The authors have scarcely seen an example in which the laminse have been 
continued without interruption around the shaft of a long bone, and in flat bones 
encircle the canal, but that they are individually thicker on the one than on the other side. Although this may 
be the case in some instances it has been but rarely seen by the authors. 
* Kolliker, page 289, oper. cit. 
t This appearance is figured by M. Kolliker, but no reference is made to the peculiarity in the letterpress. 
