Of Bones. 25 
microfcope as to (hew only the periofteum and mufcular 
fibres, which were cut tranfverfly, and appeared to be 
Surrounded by fibrils of the periofteum, as in fig. 54. where 
Y Z A B is the periofteum, and Z C D A are the flefhy 
fibres cut tranfverfly; this was part of a rib taken from 
a fat ox. 
It appears therefore from Mr. Leeuwenhoek’s obser¬ 
vation on bones of all kinds, that they do confift of ex¬ 
ceeding fmall veflels, arifing from the inner hollow or 
Spongy part of the bone, and paffing through the Super¬ 
ficial or cortical fubftance, enter the periofteum; and 
from thence are continued farther into the body, even 
to the remote parts thereof. Hence it is, that in a 
healthful body there is a conftant fupply of an oily fub¬ 
ftance conveyed into the bones; which again is con- 
ftantly carried out from the bones by means of thefe vef- 
fels into all parts of the body, even to the extremity of 
the fingers. He examined a very fmall piece of the Solid 
part of the (hin-bone of an ox, and found it to confift of 
four forts of tubes, perforated lengthways. The firft 
fort fo fmall and fo clofely united, as fcarce to be dif- 
cernable in a tranfverfe feaion of it. The Second fort 
of tubes (Some of which are four, fome fix times larger 
than the firft) are alfo difficult to be discover’d - s becaufe 
in cutting or /having the bone, although the knife wae 
(harp, it deftroyed and broke many of the tubular parts, 
which fhut up their apertures. The third fort greatly 
exceed thofe of the fecond, but were alfo difficult to be 
difeerned, becaufe the knife tore fome of them in cut¬ 
ting ; yet notwithftanding he was perfuaded, that bones 
are compofed out of fucceffive additions of rings of 
tubes, in the fame manner as wood is. The fourth 
fort are much larger than thefe, and fewer, as will ap¬ 
pear in fig. 62. whereof M reprefents a very Small piece 
@f 
