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region. Here, therefore, the innervation clearly proves 

 nothing, and it may at least be doubted whether it proves 

 any more in the case of the Elasmobranchs. We refer 

 now purely to neurological evidence, and are of course 

 aware that the supposed migration of the Elasmobranch 

 fin is alleged to be supported by ontogeny also. 



Stannius [pj). cit.) makes several references to the 

 spinal nerves of the Plaice, and he quite realised the 

 morphological value of the anterior extremity of the dorsal 

 fin, since he carefully distinguishes between the forward 

 extension of mixed spinal nerves over the roof of the 

 cranium, and the sensory dorsal branches of the cranial 

 nerves themselves. His work also contains a figure of the 

 anterior spinal nerves of the Plaice (Taf. iv., fig. 1). 



4. — ^The Sympathetic Nervous System (Fig. 26). 



Owing to the impossibility of satisfactorily dissecting 

 the anterior portion of the sympathetic, we plotted it out 

 from the same series of sections as were used in the case 

 of fig. 23. As it is drawn to the same scale, the two figs, 

 may therefore be compared. Our examination of the 

 sympathetic commenced at the sixth vertebra, and behind 

 the seventh spinal nerve. It is described from behind 

 forwards, right side first. 



The sympathetic cord may be conveniently divided 

 into two parts, which we will call the cranial sympathetic, 

 associated with the skull and cranial nerves, and the 

 spinal sympathetic, associated with the vertebral column 

 and spinal nerves. In each portion, the ganglia are 

 numbered separately from before backwards. 



At the sixth vertebra the sympathetic is situated 

 laterally below the centrum and the transverse process. 

 It here sends a short Ramus communicans to the ventral 

 ramus of the seventh spinal nerve (corn, vii.), which 



