4.76 Prof. Reid on the Vogmarus Islandicus. 
extend through the whole height of the tubes, and the light is 
transmitted freely through the transverse, and imperfectly along 
the lines occupied by the vertical walls. This remarkable texture 
enters very largely into the formation of the skeleton, being found 
not only in the bodies of the vertebre but also in the inferior and 
superior spinous processes, in the lower and middle parts of the 
interneural spines, and in much the greater number of the bones of 
the head. It is also present in the dermo-skeleton, for excluding 
those bones of the head which some regard as forming a part of 
the dermo-skeleton, it is found in the lateral line of the body. 
This texture is chiefly arranged in the form of bands or plates 
and tubes; and in the series of little elevations placed on the 
lateral line of the body it forms masses, from which branches pass 
forwards and backwards along this line. The most frequent 
form in which it presents itself is the tubular. I have stated 
that this texture is very strong, and it requires considerable force 
to break it up by the needles. It is composed of a hyaline tex- 
ture, having, in some parts at least, some pale imdistinct cor- 
puscles scattered through it, so that though in some respects it 
approaches the cartilaginous tissue, it could be very readily di- 
stinguished from the true cartilage found in some other parts of 
the body of the animal, chiefly from the absence of the nucleated 
corpuscles or cells. One of the best methods of obtaiming a good 
view of this tissue in the vertebre is to subject the parts contain- 
ing it under examination to the action of aqua potasse, which 
does not affect it, while it dissolves the surrounding texture. As 
this structure depolarizes the light, when Nicol’s polarizing 
prisms are adapted to the microscope, the difference between its 
colour and that of the surrounding textures sometimes brings out 
its arrangement very distinctly. The size of the tubes formed by 
this tissue and the thickness of their walls varies. The walls of 
some which I measured in the vertebra were about z>/59th of an 
inch thick, and the calibre of the tube was about 775th of an 
inch in its longest and 745th of an inch in its shortest diameter. 
The inferior spmous processes, and the lower parts of those su- 
perior spinous processes I examined, seemed entirely composed of 
this tissue arranged in the form of tubes similar to those in the 
vertebre, running parallel to each other, so that a longitudinal 
section of them presented a number of parallel longitudinal lines 
with spaces between them, while a transverse section exhibited a 
reticulated appearance, produced by the open mouths of the cut 
tubes. In the upper portion of the superior spinous processes, 
and the greater portion of the interneural spines, it was chiefly 
arranged in the form of one large tube, of a circular form gene- 
rally, the interior of which was, in the spinous process, filled 
up with a structure presenting all the appearance of cartilage 
having numerous nucleated corpuscles (fig. 8), while in the inter- 
Pid fe carted, 
aR WA Dv eral aims blag inca Ka eon ng) 
