( mt ) 
which are the firft Principles of the Spirits and Humors 3 
into motion, by which motion they begin a Circulation, 
and being [expanded they dilate the conteining pam, 
whofe Dilatation both caufes an Encreale in the Dimen- 
iions of the Animal, and makes them more capable of 
the Acceffionof new Particles to nourifli and augment 
them. 
Coming to defcribe the Nature and Structure of the 
Parts, which are the Subjeft of the Difcourfe, he begins 
with the Perioftium, or Membrane which invefts the 
Bones, which confifts of two forts of Fibres, one of 
which lying next to the Bone it felf, is derived from the 
Dura Mater 9 the other from the Tendons of theMufcleg, 
The ufe of this Membrane is to cover the Bones - 0 To 
convey Spirits into them for their Senfe, and to affift in 
their Nutrition, to which end it has Fibres inferred in- 
to them 5 To limit their Growth , To keep fome of them 
conjoyn'd$ To joyn the Bones and their Cartilages to- 
gether 3 to fatten the Heads and Tendons of the Mufcles 
to the Bones 5 and laftly, for the fafety and lecurity of 
the Bones againft In juries, as it ferves to make them fen- 
fible, and fc> gives the Animal a quick apprehenfion of 
■any Mifchief that threatens thofe parts, and dire&sus in 
our application of Remedies when they are injured. 
The Bones, tho they are at firft Gelatinous, and after- 
guards Cartilaginous, are when they come to their true 
and proper nature, folid and hard, confiding of terre- 
ttrial and (aline Particles. Thefe Particles, being in their 
feveral Series united at their Extremities, form Strings, 
and thefe Strings being united make diftinft Plates, 
whteh lying one over another make the whole Thick- 
nefs of the Bone. In and between thefe Plates he ob- 
ferves two forts erf* Pores, fome which run through 
every Plate, others which are formed between them for 
the Difpenfation of the Medullary Oil to the Subftance 
of the Bone. The Superficies of the Bones is unequal, 
N 2 being 
