74 SCIENCE PROGRESS. 



effect best, on stimulating at the second and third thoracic 

 seofments, and came to the conclusion that these two 

 nerves are those carrying the fibres. They further traced 

 the fibres as passing through the Gasserian ganglion into 

 the ophthalmic branch of the fifth cranial nerve. Bernard ^ 

 observed in addition a drawing back of the eyeball and a 

 fall of the eyelids after section of the nerve. By cutting 

 both the first and second thoracic anterior roots he obtained 

 the same result. Langley and, Dickinson "' showed, by the 

 nicotine method, that there were nerve cells on the course 

 of these fibres, which are situated in the superior cervical 

 ganglion. By stimulation of the anterior roots, Langley ^ 

 finds that in the dog and cat the fibres leave by the first and 

 second thoracic nerves, occasionally by the third, though 

 as a rule these latter only run to the nicitating membrane 

 and eyelids. In the rabbit the second and third thoracic 

 are the chief nerves, the first exerting but slight action. 

 There are no other nerve cells on their course other than 

 those in the superior cervical ganglion. 



Nerves to the splincte7' ij'idis and ciliary muscle, — 

 Langley and Anderson ■* have shown that at any rate the 

 main number of cells in the ciliary ganglion, are on the 

 course of the fibres to these muscles. After the injection 

 of ten milligrams of nicotine, stimulation of the third nerve 

 produces no effect, though stimulation of the short ciliary 

 nerves still produces the usual result. 



On a review of the whole of the facts of the general 

 efferent innervation of the structures developed from the 

 splanchnic mesoblast, we find that we may draw certain 

 generalisations. 



In all thoroughly investigated cases, the nerve chain 

 uniting the central nervous system with the peripheral 

 organ consists of two links, each consisting of a nerve 

 cell and its fibre. The upper one, with its cell placed 



^ Comp. Re?id., Soc. de Biol., vol. iv., pp. 155, 168, 1852 ; and Coinp. 

 Rend, vol. xxxvi., p. 375. 



^ Proc. Roy. Soc, vol. xlvii., p. 379, 1889-90. 

 * F/iii. Trans., vol. clxxxiii., p. 85, 1892. 

 ^ Jo urn. of Physiol., vol. xiii., p. 460, 1892. 



