854 
dened to be correct, the parietes of medullary 
cavity should not show colour, as here absorp- 
tion 1s sup to be going on. 
From what is already known, I think that 
the bones are coloured by the madder just in 
portion to their powers of imbibition, which 
will be in inverse proportion to the amount of 
phosphate of lime which they contain. 
As the growth of bone, the laws 
common to the growth of every other tissue 
and to the whole body will, I think, be found 
to hold good. And the growth of these organs 
will be found to be interstitial, pervading the 
whole substance, though the action will be 
more energetic at some points than at others, 
as the neighbouring organs may require greater 
length or breadth in one direction than in an- 
other. 
The younger the bone the more rapid will be 
its growth, but this law is common to all the 
tissues. The increase of length of a long bone 
at the epiphysis must not be confounded with 
growth of the bone, for here, so long as car- 
tilage connects the shaft with the epiphysis, 
osseous tissue is being developed; whereas, in 
speaking of the growth of bones, the increase 
of the tissue already developed is alone meant. 
Of the developement of osseous tissue.—As 
the developement takes place in cartilage, and 
as the cartilage undergoes some change pre- 
vious to its giving place to bone, it will be 
well to give a slight sketch of the structure of 
temporary cartilage before going into the for- 
mation of the more permanent tissue. The 
rudimentary condition of cartilage may be best 
examined in the feetal chicken, a few days 
after the commencement of incubation. The 
exact time for making the observation will be 
found by taking an egg for examination every 
six hours, commencing after the eggs have been 
exposed to the due temperature for thirty-six 
hours. On the first appearance of the verte- 
bral column, which will present a semitrans- 
nt line in the length of the developing 
cetus, the whole must be removed with great 
care to the field of the microscope. This part of 
the operation requires some care, but with a little 
management may be successfully performed. 
I found but little difficulty in removing the 
delicate object after adopting the following 
plan. Having, in the first place, placed the 
egg in adish of water of sufficient depth to 
cover it, letthe shell be carefully removed ; then, 
by moving the water with the assistance of a 
camel’s-hair brush, take away the albumen so 
as to leave the yelk free. The point where deve- 
lopement is going on will then be sufficiently 
conspicuous. Ata considerable distance around 
this the membrane of the yelk should, with 
a pair of sharp scissors, be cut through, and 
carefully separated with the aid of a camel’s- 
hair brush and a pair of forceps. This having 
been effected, the subject for examination will 
be left on the surface of the yelk, and may, 
with delicate manipulation with the pencil, be 
removed to a slip of glass held near it under 
the surface of the water. Having completed 
your purpose so far, the glass must be raised 
OSSEOUS TISSUE. 
very slowly from the water, so that the spe- 
cimen may not float off, and this being covered _ 
with a little thin tale or glass supported at the — 
sides, so that it shall not upon the em- — 
bryo to be removed to the field of the micro- 
scope. If the specimen be favourable, the — 
semitransparent line of the vertebral column 
will under a low power a’ made up of a 
vast number of clear colourless oval 
closely pray Bc a. no appreciable 
8 between the indivi composing the 
saan: Under a higher power, however, each 
cell will present a definite outline with a central 
nucleus or rmee and even in oy nucleoli 
The cells give appearance of density 
clearness \Pecbinances and with their d 
and smooth outline present a 
the highly granular cells of developement tha 
surround them. In each vertebra there it 
some show of a radiate arrangement, for mar 
cells are egg-shaped, and have their small 
placed towards the centre of the Care ‘ 
At this period of the formative Cs cell: 
are so close to each other that is no spac 
for intercellular tissue. i 
With the growth of the embryo the cartilag 
advances, and its developement as a perfe 
tissue is completed by the of | 
cells from each other by the interposition 
an intercellular tissue. This latter is tra 
parent and dense, but without traces of di 
nite structure, unless it be a minutely rant 
tissue. Temporary cartilage is thus shown 
be composed of cells having parietes and ¢ 
tents, and intercellular, (see fig. 457) or, as Se 
have called it, hyal 
substance, 
which the cells or 
puscles areeq uli i j 
tributed. In carti 
preter 
evelo of 
eam ne 
commencement of 
developement of 
great changes oe¢ 
the arrangement ¢ 
cartilage COPD > ] 
the immediate 
a, temporary carti- dents of ossifi¢ 
lage, with the corpus- They are no 
cles and _ intercellular equally distri 
tissue; 5, tempo te 
cartilage, with eae through the * 
puscles forming for ossi- Substance, but 
fication. found arranged 
rallel columns of 
ble lengths, in the line of the length of the 
The corpuscles forming into columas 
sarily leave intervening columns of i 
lular tissue. A notion has pretty ge 
prevailed that the corpuscles already 
marshal themselves into this order. . 
however, that on further investigation 
found that each corpuscle has developed 
and that they have been developed 
direction only, and that towards the 
where osseous formation has commence 
we find that the first perceptible chal 
we 
