■[22 MESSRS. J. TOMES AND C. DE MORGAN ON THE 
nebulous outlines. On the other hand, if we have light passing from all sides 
obliquely through the preparation, that is, if the object be illuminated by a hollow 
cone of light, in the manner obtainable by Mr. Gillbtt’s arrangement of achromatic 
condenser, or by rendering opake the centre of the lower lens of the ordinary achro- 
matic condenser, the fibres disappear, and we see in their place a granular tissue, 
with a tendency here and there to a linear arrangement of the granules, and the 
lacunee and canaliculi clear and distinct, when well in focus, but with a fibre-like 
nebulosity when slightly out of focus, especially in those parts where the latter run 
obliquely through the specimen. This is more especially the case where the cana- 
liculi are filled with fluid, or where they have become solid, a condition very common 
in the bones of old subjects. Indeed, in many specimens where the bone is not highly 
developed, a fibrous appearance at once strikes the eye, and it is only on careful exa- 
mination of the surface of the section that the illusion is dispelled by the orifices of 
the canaliculi appearing at the termination of the apparent fibres. Amongst a great 
many examples the authors have not seen an instance in which the fibrous appear- 
ance could not be traced to canaliculi, this effect being often increased by the pre- 
sence of granules. If parallel dentinal tubes be viewed by a side light, in the manner 
we have described, each tube will throw two or three strong nebulous lines, which 
might be mistaken for fibres ; and if tubes cut transversly be inspected in a similar 
manner, each will appear to have several concentric lines extending half round it on 
the side opposite to that from which the light proceeds. 
That the presence of granules imbedded in a less refractive tissue may, when 
viewed by a side light, give an appearance of fibres, is shown on an examination of 
pus-globules under similar circumstances, when each globule will seem to have 
a striated surface; and that slightly rounded prominences will produce a like 
effect is shown in the case of some species of Navicula. The surface of these latter 
objects is marked by rows of slight prominences, which, when the light is oblique 
and passes through the specimen from one point only, appear as lines or fibres, the 
direction of which will change with alteration in the direction of the light ; that is 
to say, shadows will extend from one eminence to another in the opposite direetion 
to that from which the light enters. If we examine the projecting spiculse of bone 
forming in temporary cartilage under corresponding conditions as regards light, a 
similar fibrous appearance will be developed. 
Under these circumstances the authors are forced to the conclusion that bone 
substance, instead of being made up of minute reticulate fibres, is composed of 
granules or granular cells, imbedded in a more or less clear homogeneous oi subgra- 
nular matrix. This subject will receive further elucidation under the head of deve- 
lopment. These views are supported by the appearances presented not only in deve- 
loping bone of young subjects, but also in the bone of adults. 
Thus as regards the basement homogeneous tissue, it will be found that where 
lamination is highly developed, the larninse have a transparent and structureless, and 
