56 THE SALAMANDER 



(i) The fibres of the caput laterale (m.l.b.s'.) pass obliquely antero- 

 laterally and are inserted along the lower eyelid from a point immedi- 

 ately anterior to the insertion of the pars principalis to about the 

 centre of the eyelid. 



(ii) The fibres of the caput me di ale (m.l.b.s".) pass antero-mesially 

 and are attached to the side wall of the skull immediately ventral 

 to the origin of the pars principalis. This portion loops across the 

 origin of the M. retractor bulbi. 



(<:) The pars transversalis (m.l.b.t.) takes its origin from the side 

 wall of the skull — mainly from the lower edges of the frontal and 

 parietal — anterior to the insertion of the caput mediale^ pars sagittalis^ 

 and ventral to the origin oi\h^ pars principalis. Its fibres are the most 

 ventral of all, and pass across the anterior portion of the floor of the 

 orbit forming an arch which is convex anteriorly. They are inserted 

 on the lower eyelid anterior to the caput laterale^ pars sagittalis^ and 

 on the maxilla. 



Innervation : All sections are innervated by the second branch of 

 the trigeminus nerve (Vg) in the Salamander. 



Function'. The muscle as a whole appears to have at least two 

 principal functions : (i) as levator bulbi, (ii) as accessory respiratory 

 muscle by enlarging the mouth cavity. It may also serve as an 

 adductor of the lower lid, but the movement thereby caused must 

 be very slight, even if it exists at all (cf. Johnson, 1926). 



4. Muscles of the Seventh Nerve. 



As already mentioned, an accurate description of these muscles in 

 both larva and adult, illustrated by excellent figures, was published 

 by Driiner in 1901. He divides the muscles supplied by the Vllth 

 nerve into two groups, according to whether they are supplied by the 

 nerve before., or after^ it has received the R. communicans IX+X ad 

 VII, on the supposition that this ramus contains motor fibres. By 

 comparison with the condition in other Urodeles this conjecture 

 appears unwarranted, and it seems more likely that the R. communi- 

 cans contains only general cutaneous and communis fibres, and there- 

 fore has no influence on the muscular supply. Driiner's classification 

 is accordingly unnecessary. 



M. depressor mandihulae (Edgeworth). 



Depressor maxillae inferioris .... v. Siebold (1828). 



Temporo-angulaire ...... Duges (1834). 



Digastricus Fischer (1843); Stannius (1854-6); Osawa (1902}. 



Digastrique .... Cuvier (1835); Rusconi (1854). 



