OPENING ADDEESS. 9 



1801 by St. Hilaire and repeated by Meyer in 1843 and 

 de Lamballe in 1858. In 1822 Blainville pointed out the 

 fallacious character of the inference. The organ had been 

 correctly described some years before and Leydig in 1850 

 showed that it forms a central terminus for a series of 

 glandular tubes which run over the surface of the body of 

 the fish. It is incapable of generating any electromotive 

 change in response to a stimulus, and McDonnell's infer- 

 ence was therefore unsound. Here we have an instance 

 of the failure of the inference from supposed structure 

 inadequately examined. The organs in question form 

 part of what Leydig and others have called the sensory 

 canal system. You see the difficulty of getting clear of 

 this tendency to infer function. It is a canal system, but 

 as far as I can make out the only evidence in favour of it 

 being a, sensory canal system is that the nerve which supplies 

 it, is said to be the 5th cranial which, in higher animals, is 

 mainly a sensory nerve, and that cells resembling those in 

 sensory structures are present in some of its terminations ; 

 but there is no physiological ground that I know of for the 

 functional assumption. The activities of the organ and of 

 the gland tubes connected with it are to this day unknown, 

 since appropriate physiological experiments have not yet 

 been devised to ascertain them. Yet unwarned by the 

 experience of de Lamballe and McDonnell the structure 

 has been very generally given the functional attributes of 

 a terminal sensory organ. It may be merely secretory, 

 and indeed Fritsch and others have urged this, but let us 

 not commit another jump into the abyss ; physiological 

 enquiry in conjunction with anatomical can alone deter- 

 mine what these organs really do.* (SeeFritsch; Berlin 



* In the Section of Biology at the meeting of the British Association, 

 Oxford, 1894, Mr. Collinge brought forward anatomical evidence to show 

 that the nerve supplying the canal system of Elasmobranchs is not the 5th 

 but the 7th Cranial Nerve, i.e., an efferent or motor one ! ! 



