STRUCTURE AND DEVELOPMENT OF BONE. 
117 
imparting a peculiarity to the tissue which cannot fail to be remarked. The presence 
of persistent nuclei in the lacunas has been questioned by recent authors ; some state 
that they may be detected at times, while others regard their presence as very pro- 
blematical. Mr. Goodsir* describes the lacunae as containing a little mass of 
nucleated cells. 
M. Kolliker'I', after citing Schwann, Krause, Kohlrausch, Heischmann, Gun- 
ther and Bonders, all of whom believe in the persistence of the nuclei in the lacunae, 
goes on to say that he has paid great attention to the subject. In the bones of an 
individual eighteen years old he found them after the sections had been treated with 
acid. The authors have had no difficulty in finding the nuclei in recent bone with- 
out the aid of chemical treatment. If a small fragment be taken from the spongy 
portion of a fresh bone and freed from adherent fat, the nuclei may be seen as small 
rounded bodies attached to the walls of the lacunse ; their appearance is shown in 
Plate IX. figs. 27 and 29. In dry sections of bone the nuclei are less readily 
recognized, although we may find them here and there. The authors have sections 
of a fossil bone from the Wealden (supposed to be Pterodactyle) in which all the 
lacunae have well-defined nuclei (Plate VII. fig. 14). 
Haversian Systems . — Having described the several parts entering into the forma- 
tion of Haversian systems, it now remains to say a few words on the relations of these 
to each other, and to the other parts of bone which are not included under that term. 
The union of the Haversian and other systems of laminae is seen, in a transverse 
section of a long bone, to be effected by the interposition of a layer of transparent 
tissue. In a recently-formed system the canaliculi do not appear to pass through 
this layer, but in older ones they are seen to pass across from the external lacunae 
and to anastomose with those from the interstitial or circumferential laminae, or with 
those of adjoining Haversian systems (Plate VII. fig. 10). After these intercommuni- 
cations have been fully established, the connecting layer loses something of its origi- 
nal transparency, but not the whole, for in the bones of aged subjects it may still be 
distinguished. 
In Dr. Todd and Mr. Bowman’s ‘Physiological Anatomy,’ it is stated, on the au- 
thority of Mr. Tomes, that the canaliculi of adjoining systems anastomose but scantily. 
A more extended examination into the subject has shown this to be true of the more 
recently developed systems, but not of those of greater age. In addition to the con- 
nection of systems of laminse by the juxtaposition of their external members, instances 
not unfrequently occur where several Haversian systems, linearly arranged, are encir- 
cled by a series of laminse common to the whole. This is shown in Plate VI. fig. 5. But 
although we may find groups of systems thus bound together by enclosing laminse, in 
addition to the general or partial investment by circumferential laminse, such binding 
together is clearly not necessary to ensure the strength of the bone, as we see many 
* Anatomical and Pathological Observations, by John Gooosib and Henby D. S. Goodsik, 1845, 
t Kolliker, oper . cit . p. 296. 
MDCCCLIII. R 
