Royal Society. 469 



has been seen too that it not unfrequentljr happens that a series of 

 Haversian systems is contained within a common series of surround- 

 ings laminae. Sometimes the Haversian systems are rendered quite 

 solid by the narrowing of the Haversian canal and ultimate develop- 

 ment of a mere lacuna in the centre of the system. The more re- 

 cently developed Haversian systems, which occujiy the Haversian 

 spaces before described, are seen to be darker in colour than the 

 older ones, from the greater aliundance of canaliculi, and the more 

 general granularity of the tissue. 



5. Ossified articular cartilage. — This structure the authors have 

 found in all the joints which they have examined, in the lower jaw, 

 amongst others, where KoUiker failed to detect it. Towards the 

 bone the tissue becomes in general granular and of a brownish colour 

 and usually there is a distinct line of demarcation between the bone 

 and the ossified cartilage ; but sometimes they graduate insensibly 

 the one into the other. 



Towards the articular surface the margin is even and regular ; but 

 towards the bone it is deeply indented, from the bone advancing into 

 it by rounded projections. Hence the articular cartilage varies in 

 thickness. The authors believe that this, so far from being an indi- 

 cation of imperfect development, is in reality an evidence of design, 

 and intended to give an uniform and unyielding surface for the car- 

 tilage to rest upon. 



6. Ossified cells. — In the bones of aged people it is frequently ob- 

 served that they become light and spongy, and after maceration con- 

 tain a white powder in the cancellated structure. 'I'liis powder the 

 authors have found to be composed mainly of ossified nucleated 

 cells, either detached or held together in masses. They are spherical, 

 and contain a dark granular nucleus, which is surrounded by a thick 

 transparent wall. 



If portions of the cancelli be examined, they will be found to have 

 similar cells adherent to their surfaces, or to those of the Haversian 

 canals, with here and there canaliculi of adjoining lacunae shooting 

 into them, while the nuclei have themselves assumed the form of 

 lacunae. Similar cells may be found imbedded in parts of most sec- 

 tions of bone. In order to see this condition clearly, it is desirable 

 that the sections and the loose cells should be mounted in Canada 

 balsam. 



7. Bone tissue. — The views generally entertained with regard to the 

 ultimate structure of bone tissue arc, the older one, that it consists 

 of an aggregation of granules in a transparent matrix ; and that 

 which has been more recently put forward by Dr. Sharpey, that in 

 many cases it is composed of ossified decussating fibres. 



The authors have satisfied themselves that the ultimate structure 

 of bone tissue is composed of minute granules or granular bodies 

 imbedded in a clear or subgranular matrix ; and that the aj)pearance 

 of fibres is due in many cases to the mode of illumination. By 

 transmitted light passing through them in the long axis of the mi- 

 croscope tlie preparations show a granular or a structureless apjjcar- 

 ancc, or alternations of a granular and structureless part. ]Jut under 



