( 95 ) 
l had another (mail piece of Bone lying before a 
Microfcope, of which I caus’d a part to be reprefenred 
by R S W X t V, Fig. 3. j n which RSTF is the 
Bone, and S W X T the ^erioftcum^ which in this place 
was no thicker than a thick Hair of a Man’s Beard, 
but in another part of the lame Bone at a fmall di- 
Bance, it was full four times that thicknefs 
1 placed another piece of Bone before a Microfcope 
in fuch a manner, as that the Bone did not appear, 
but only the Periofteum and the Mufcular Fibres, which 
were cut thro’ tranfverfly, and appear’d to be furroun- 
ded by the FibrilU of the Peno/feum, as is reprefenred 
by TZ C D A B, Fig. 4. where TZ A B is the Perio* 
ft cum, and ZC DA are the flefhy Fibres cut thro’ tranf- 
verify. This piece of Bone was taken from one of the 
Ribs of a fat Ox, and I was furpris’d to find, that in 
this place, as I cut longways thro’ the Rib, I could not 
diicover any Particles of the Marrow, whereas in other 
parts the Rib abounded with them. 
NotwithBanding. the great number of Obfervations 
that i have made upon the Bones, and the Membrane 
that furrounds them, which is commonly call’d the 
Ptriofteum , 1 have never been able to fatisfy myfelf 
entirely about them* I Bill imagin’d, that the part of 
the Periofteum , which immediately covers the Bone, 
and is Bridtly united to it, muft have a degree of 
hardnefs approaching to that of the Bone, and that at 
a fmall diftance from the Bone, the Perioftcum mull 
have a foftnefs and flexibility like that of the carneous 
and adipofe Membranes. 
[ had lying by me four pieces of Ribs of a fat 
Ox, which 1 had kept by me full two Months, and. 
which were now grown very dry. From one of thefe 
I. tore off the Periojleum, which I found Buck much, 
harder; 
