( "8 ) 
them; to which thefe Bortes did perform the OiEce of a 
Trochlea, 
The Firfl Pair of Mufclesii£N^'\\\c\i firft came to be dif- 
fe(3:ed, upon the Pronation of the Animal, and from its 
Figure, I ihall call, Triangularis) arifes Fkfhy from the 
whole Length of the internal Side of thefe Bones^ and in- 
ferred their oppofite Tendons on each fide of the Rima, 
or Aperture of the Marfupium. Under part of thefe 
Mufcles, lay another^ or a Second Pair; flat and thin ; 
having ih^'ir Origin from the upper Part of the internal 
Side of the OJfa Marfupialia and itiferting their oppofite 
Tendons a little above the Tendons of the rormer Mujcles^ 
the Tendence or Direction of the Mufcular Filres oi this 
Pair, in Relation to the Firft, made a DecufTation. The 
Third Pair of Mufcles we lhall take notice of, had their 
Rife from the Fore-part of the Bafis of thefe Bones ^whttc 
they were jointed to the Os Puhis ; and were afterwards 
inferted into the Linea Afpera of the Thigh-Bone. The 
Fourth Pair did arife from the external Side of thefe 
Bones near the Bafis, and are injerted into the Fore Part 
of the Thigh-Bone near the middle. 
The Lafl Pair of Mufcles I hinted at, (to which I 
thought thefe Bones might perform the OfBce of a Tro- 
chlea^ or PuHy) arifes more immediately from the Mar- • 
fupium or Pouch it felf : For fpreading their Mufcular Fi- 
bres all over this Bag^ as they ifTue from it, by joining 
their Fibres together they more remarkably form a 
foJid Mufcle ; w^hich of each fide pajfing over the middle 
of thefe Bones^ (i. e. in the prone Pofture we are difled:- 
ing it ) at length were inferted into the Spine of the Os 
Hit. 
By confidering the Strudure of thefe Mufcles, and 
what muft be the EfFed: of their Action or Contraftion ; 
' one cannot but think the Two FirH muft ferve towards 
the Dilatation or opening this Marfupium or Pouch : For 
