138 E. A. SCHAFER. 



bundles which overlie them, being in fact of a very charac- 

 teristic aspect (Plate VIII, fig. 2). Their straight course and 

 their stiffness of aspect are alike remarkable; in these respects I 

 can only compare them to the fibres of which the basilar mem- 

 brane of the cochlea is composed, and which are possibly of a 

 similar nature. 



The osteogenic fibres of a bunch diverge from one other, the 

 intervals between them are occupied by the irregularly-shaped 

 osteoblasts. The fibres appear to be angular in shape, and the 

 ends of the osteoblasts are flattened and are applied to the 

 fibres which they lie between. 



Since the osteogenic fibres diverge from the end of a spicule, 

 those which are situated laterally come in contact with the 

 similarly divergent fibres of the neighbouring bunches. When 

 this is the case their extremities may meet and blend, and 

 some of the fibres from one spicule may thus pass continuously 

 into those from another spicule (see fig. 2, Plate VIII). But 

 the majority do not thus blend, but pass across one another's 

 direction at a more or less acute angle, and thus present an 

 appearance of lattice-work like that of the intercrossing fibres 

 of perfect bone, except that in their present condition the fibres 

 are more distinct one from another. Meanwhile the calcific 

 deposit gradually extends from the already calcified spicule into 

 the clear and soft osteogenic fibres and also into the osteogenic 

 substance which here cements the fibres together. The earthy 

 deposit may also make its appearance in isolated patches on the 

 fibres, a little in advance of the general area of ossification, but 

 these are soon united to the rest by an extension of the calcifi- 

 cation along those parts of the osteogenic fibres which bridge 

 across the intervening space. In this way the first bony 

 lamella becomes formed, and while it is thus becoming extended 

 peripherally it undergoes a process of thickness pari passu at 

 its central part by a formation of other lamella3 upon its surface. 

 These, like the first, are preceded by osteogenic fibres which 

 shoot out at numerous points from the surfnce of the bone 

 which is already calcified ; they form in a similar way systems of 

 intercrossing fibres, and the earthy deposit gradually extends 

 itself along them and in the intervening soft osteogenic sub- 

 stance. While in this manner layer upon layer of the flat bone 

 becomes formed, two kinds of spaces are left, those which are to 

 become respectively the lacunae and the Haversian canals of the 

 bone. The mode in which these are produced has been so often 

 and so carefully described that it is unnecessary to dwell upon 

 it here. It is sufficient to remark that the Haversian canals, 

 large at first and enclosing besides a blood-vessel a quantity of 

 osteoblastic tissue, become gradually narrowed by the deposit of 



