STRUCTURE AND DEVELOPMENT OF BONE. 
121 
of the tissue takes its place, and must be regarded as the general condition of bone*. 
Dr. Sharpey, when he formed this opinion, had directed his attention principally to 
thin fragments torn from the surface of bone macerated in hydrochloric acid. The 
authors have seen the appearance both in decalcified bone, and in sections which 
have not been chemically treated ; but they believe the fibrous appearance to be an 
optical effect produced by the canaliculi and granules when the light is unequally 
distributed, or the object-glass in bad adjustment. It will be shown in the subse- 
quent details, that the appearance can be produced and dispelled at pleasure by 
alterations in the direction of the transmitted light. If thin sections of bone are seen 
by transmitted light (passing through in the axis of the microscope,) the tissue will 
appear either granular or structureless, and in the laminee alternations of granular 
and structureless parts will be seen. But if the light be allowed to pass in one 
direction only, and with considerable obliquity through the specimen, then the 
appearance of extremely minute fibres will present itself ; and this not only in adult 
bone, but in the isolated cells of old and in developing young bone. They are 
most strongly marked over the lacunae ;■ to which, and to the canaliculi, a confused 
and broken outline is given. The fibres appear as though arranged in series of 
short and broken lengths, parallel, and without plaiting. If the specimen be 
a little out of focus there will be an appearance of reticulated fibres marked by 
dark appearance ; the subsequent or secondary deposit, on the other hand, is quite transparent, and of a uni- 
form and homogeneous aspect, without obvious granules. This begins to cover the granular bone a very short 
distance (about the g^oth of an inch) below the surface of ossification, and, as already stated, increases further 
down. The lacunae first appear in this deposit ; there are none in the primary granular bone. In what further 
regards the nature and formation of the secondary deposit, my own observations lead me to differ considerably 
from the views of Mr. Tomes. He supposes that it is formed of cells which become impregnated with earthy 
matter, — the cartilage cells in the first instance, and afterwards the cells newly formed in the blastema. Now 
although certain appearances render it not improbable that there may be a layer of flattened and calcified cells 
next to the surface of the granular bone, I am nevertheless disposed to think that the subsequent and chief part 
of the deposit results from the calcification of successive layers of fibres generated in the blastema, and possibly 
derived from the granular cells, some cells being perhaps also involved along with the fibres, as in the ossifica- 
tion of the flat bones of the cranium : in short, it appears to me that the deposit in question is formed after 
the manner of intramembranous ossification already described (page 150). I infer that such is the process 
from the structure of the layers, for they are made up of fine reticulated fibres like the lamellse of perfect bone 
shown at page 143.” 
* On this point Kollikee, oper. cit. p. 289, observes, “ Die Grundsubstanz der Knochen besteht nach 
Sharpey und Hassall aus einem Netzwerk feiner Fasern mit rhombischen Maschen, von welchen Fasern ich 
weder an frischen, noch an mit Reagentien behandelten Knochen eine Spur habe entdecken konnen. Was 
Arnold neulich Primitiv-fasern der Knochen nennt, sind, wie seine Abbildungen lehren, nur die Granula der 
Grundsubstanz, an denen er eine lineare Aneinanderreihung zu erkennen glaubt, und seine Querstreifen auf 
Flachenschnitten, und radiaren Linien auf QuerschlifFen, wenigstens die letzteren sicher, nichts als die Auslaufer 
der Knochenhohlen. SoUten durch irgend ein Reagens in dem Knochengewebe deutliche Fibrillen nach- 
gewiesen werden konnen, was mir aber noch nicht gelungen ist, so konnten dieselben wohl keine anderen sein, 
als diejenigen, welche in ossificirenden Knorpel das streifige Ansehen bewirken und die von Sharpey und mir 
bei der Knochenbildung aus dem Periost beschriebenen.” 
