f ru ) 
^/^//wWj from fuchNitro-aerial particles put into Motion; fo 
in this cafe, the Heat given by the incubating Bird, and received 
and detained in the albumen , is thence collefied by the many 
fmall fuckers of the Umbilical vefTels, and fo conveyed to the 
Chicken. Upon which ground he undertakes to folve that di- 
fficult ^uere^ viz, Why a f£tm after 'tis born and yet do fed 
in its Membrans^may yet live for fome hours \ whereas ifbewg de^ 
vejied of thofe skjnsy it have once taken jiir into its Lungs ^it can • 
not live a moment after vpithout /A<?Which he anfwers thusjThat 
a fatus horn^ and yet wrapped clofe within the membrans,is in 
a like ftate>and breaths much after the fame manner, as a chick 
includedinan Egg.But if, thofe membrans bemg pulled away 
from thefatus^it do,for breathing, mth labour contraft the muf- 
ctes of theCheft and the Midriff, it fpends in that mufcular la- 
bor much more of thofe nitro-aerial parts than before ; whence 
there is a greater necefTityfor thtfatus to breath in the open 
Air, there being now nothing to compenfate the defefl of thac 
refpiration. 
But enough alfo of this Exercitation ; let us pafs to the laft^ 
which is of Mufcular motion^ and Animal SfiritsJTis undoubt- 
ed, that the Motion of Animals is made by the Contraftion of 
the Mufcles i but 'tis controverted, in what manner that Con* 
traftion is madef Themoft received opinion is, thattheFibres 
of the Mufcles are inflated by fome Elaftique matter, fwelling 
them as to theirbreadth^buc contrafting them as to their length; 
though the Learned Steno in hisMyology thinks it needlefs/ to 
take in a Springy matter for the Contradion of the Mufcles ; 
forafinuch as he judges it may beefre<3:ed by the foleChange of 
their Figure, Concerning which our Atithor confiders, that it 
appears not; i.How that Motion,requifite to make a change ia 
the Figure,can be produced without the acceffion of fome new 
matter. 2. How it coms to pafs,if no new matter enters the muf- 
cle, that in its contraftion it is fo fenfibly hard and tenfe ? And 
whereas Anatomifts have hitherto taught, that theCarneous Fi- 
bres chiefly make theContraftion in mufcles,our Author thinks 
it more probable, that the jFVi'r/V/if, transverfly inferted into 
the greater Fibres^ perform the chief part in that contraftion, 
by reafon as well of their pofition^as their Czeand number. And 
as 
