136 THE SALAMANDER 



with the oculomotor nerve in the Salamander, and it is probably of 

 a sympathetic character, and is not connected with the fibres of the 

 nerve itself. The present investigation has, however, not revealed 

 its exact relations (cf, p. 183). 



(d) Both Schwalbe and von Plessen and Rabinowicz state that the 

 oculomotor nerve sends a branch into the M. retractor bulbi. Now 

 while a twig has been found which leaves the nerve together with, 

 or close to, the ramus communicans ad V, passing amongst the fibres 

 of the above-named muscle towards the bulbus, it is improbable 

 that it terminates within the muscle, but seems rather to pass to the 

 eye itself and enter the sheath surrounding the optic nerve. Gaupp 

 reports a similar twig in the Frog. It may be that this nerve is of a 

 sympathetic nature and is associated with the ganglion above re- 

 ferred to, but on this point there is no definite evidence. 



The above account agrees fairly closely with Coghill's 'Case A' 

 and appears to represent the most usual arrangement, although indi- 

 vidual variations are quite common. They chiefly concern the mode 

 of branching, and the relations between the ramus inferior and the 

 trigeminus branch, and the exact position of the ciliary ganglion. 



IV. N. Trochlearis (n.4) (somatic motor+sensory fibres?). The 

 exact relations of this nerve are exceedingly difficult to determine by 

 dissection, partly on account of the fineness of the nerve itself and 

 the toughness of the tissue in which it is embedded, and partly on 

 account of its great variability, even on opposite sides of the same 

 animal. The discrepancies between the several published accounts 

 testify to this. 



As above mentioned, Schwalbe was the first to recognize its exis- 

 tence, but in spite of his account von Plessen and Rabinowicz state 

 that the M. obliquus superior is innervated by the trigeminus. Hoff- 

 mann (1902) gives a detailed description of the nerve, but describes 

 two anastomoses with the Vth nerve, whereas only one has been found. 



So far as the present author has been able to observe, the most 

 usual arrangement is as follows. The nerve leaves the brain near the 

 middle line immediately in front of the cerebellum, emerging on the 

 dorsal side from the deep groove which exists between this part of 

 the brain and the corpus opticus. The nerve passes antero-laterally 

 through the cranial cavity, and in doing so is often closely applied to 

 the under-surface of the parietal bone, so that great care must be 

 exercised in removing the roof of the skull to avoid damaging the 

 nerve. It emerges from the cavum cranii through a very oblique 

 foramen in the parietal, or between the parietal and the orbito- 



