470 AUGUSTA LAMONT ON 



Jacobson described only three while mentioning five, and thus ignoring the work 



Of MlESCHER. 



Retzius (1847), who investigated "the supposed electric organs" in Raia batis 

 and Squalus acanthias, also described four pairs, and concluded from their rich 

 nerve-supply that Jacobson's theory as to their sensory function was correct. 



Stannius, in his memoir on the Peripheral Nervous System of Fishes (1849), 

 describes for Plagiostomi the innervation of the ampullary system, which he alludes 

 to throughout as a " mucus-secreting apparatus." He gives an account of the innerva- 

 tion of the ampullae by the ophthalmic and buccal branches of the trigeminus, and 

 by the hyomandibular and mandibular branches of the facialis. He describes a single 

 nerve-thread, composed of eight or ten fibres, as entering each ampulla, and admits 

 his failure to have discovered anything definite regarding the nerve-endings. Spinaoc, 

 Raia batis, and R. clavata are mentioned as subjects of the investigation. 



The work of H. Muller (185 1) was in many respects an advance on that of his 

 immediate predecessors. He appears to have written largely with the object of 

 refuting the suggestion of the existence of a relation between the follicular apparatus 

 of Torpedo and electricity production, by means of a comparison with the mucous 

 canals of other Plagiostomi. He clearly distinguished between the different systems 

 of canals, and recognised that the ampullae and their tubes were confined to car- 

 tilaginous fishes, inclining to a belief in the sensory function of the system. He 

 described in more detail than previous workers the distribution of the ampullary 

 canals, especially in the genus Raia, of which he investigated three species. He 

 points out the pigmentation and wide distribution of the canals of R. vomer * com- 

 pared with the more restricted distribution and hyaline appearance of those of 

 R. undulata and R. asterias.]' 



.Leydig, who did much to advance knowledge of the ampullary canal system, 

 contributed between the years 1852 and 1868 several publications dealing with the 

 subject. He investigated, in considerable detail, the structure of the ampullae in 

 various Elasmobranchs, contributing much that was new regarding their histology, 

 innervation, and vascular supply. He maintained, throughout, the sensory function 

 of these organs, and concluded that they are organs of a sixth sense adapted for life 

 in water ; suggesting, however, that secretion might take place in association with a 

 sensory function allied to that of touch. In this connection he raised the question 

 as to whether similarly among the sweat-glands of mammals there may not be some 

 which have a more direct relation to the nervous system than to secretion. 



Contemporaneous with the work of Leydig was that of Lamballe, Eckhard, 

 and M'Donnell, the two first of whom both published the results of their investiga- 

 tions in 1858. 



Jobert de Lamballe appears to have been ignorant of any of the work of his 

 predecessors on the subject of the ampullary canal system, with the exception of an 



* Raia vomer, Mull. = R. uxyrhynchus, Linn. t Raia asterias, Mull. = R. maculata, Mon t. 



