( 37» ) 
" MiirofcoficAl Ohfervmons of Mr. Leewenhoeck , cencerniiig the- 
Optic Nerve, communiuteito the Publijher in Dutch, ar^ibf 
^ him made EngVifh» 
H Av^ng^cqmmGd'Dr. Schravefande^ tbat I could perceive no 
cavity in the Oj?tic Nerve, he told me, that GaUfg had on a 
clear Sun-lliiny day feen a hollownefs therein, encouraging me lo 
view that Nerve again with more attention. 
I took therefore, afreflb , eight diftinft 0/>//V A1?;>'z^^i , and ob- 
Terved, that after thofe Nerves had been but a little while cut off 
from the Eye, the filaments, of which they are made up, did flirink 
up , which flirinking cannot be fo much on the external furface or 
coat of the Nerve, as 'tis of the filaments that lie within the fame r 
And upon this fhrinking up, alittlepiccomesto appear about the 
middle of the Nerve j and 'tis' this pit in all probability, that 
Galen took for a cavity. This I have remarked on all occaficns. 
. Having lately viewed again an Optic Nerve , I not only faw the 
lately-mentioned little pit, but noted alfo feveral other places funk 
in, as if each filament had been in the midft drawn inwarqjls , after 
the manner by me defcribed elfewhere. 
I have alfo found, that this Nerve^ when I kt it be dried , was 
| lefs in thlcknefs than before^ fo much of it being dried away. 
Thefe Obfcrvations invited me to endeavour to dry an Optia 
iWrw, and to take care , that the fame in its drying all at once, 
might retain ( as much as w^s pofTible) the fame roundnefsand 
thicknefs all over, as the Nerve had when it was firft taken out of 
the Eye ; confidering that if there were a hollownefs in it,it would 
then difcover it felf. 
Having then dried fuch a Nerve^ and made a tranfverfe fegment 
thereof, I not only fawin it a hole, but very many, which made it 
refemble a Leathern Sive, wherein are big and fmall holes, only with 
this difference,that the holes in the Nerve were not, round(no more 
than they are not all of the famebignefs) nor fo regularly pofited 
by one another J as the holes in a Sive are ; But this piece of the 
Optic Nerve^ together with the holes therein, is more like a piece 
of Parchment in which are made holes clofe unto one another, and 
the fame mo; fined , and fo ftretchtoutj whereby the holes in the 
Parchment keep not that roundnefs, which they had before moi- 
ikning, Thefe holea or cavities being in the dried Nerve y I am 
of 
