No. I.] THE VERTEBRATE EAR. 239 



series alone, and endeavoring from their very imperfect knowl- 

 edge of its morphological relations to understand its physiolog- 

 ical laws, we would, doubtless, be much nearer than we are to- 

 day to an adequate understanding of human audition. More than 

 four centuries before Christ, Empedocles is said to have referred 

 the auditory impressions to the cochlea. In our year, a.d. 1891, 

 we are not able to do much more, notwithstanding our accumu- 

 lations of anatomical details. 



About all we know of audition is : ist, That the ear is the 

 auditory organ ; 2d, That the sensory hair cells (auditory nerve 

 origin cells) of the ear are in some way instrumental in trans- 

 forming wave motions into auditory sensations. 



The amount of experimental knowledge of the functions of 

 the lateral line organs is very limited indeed. Wiedersheim 

 summarizes the contributions to the subject in the following 

 words {loc. cit. p. 363) : "Was nun die Wii'kimgsweise der Ner- 

 venhiigel und ihre verschiedenen Modificationen bei Fischen und 

 Amphibien anbelangt so kann ich fiiglich absehen von einer 

 Erorterung der von den verschiedensten Seiten dariiber auf- 

 gestellten Hypothesen. Mit voller Sicherheit lasst sich dariiber 

 nichts behaupten, die grosste Wahrscheinlichkeit hat jedoch 

 die von Merkel aufgestellte Ansicht, nach welcher es sich 

 keinesfalls um einen chemischen, sondern nur um einen inccJiani- 

 schen Reiz (Erschiitterung des umgebenden Wassers .-') handeln 

 kann." " Wir hatten also Tastorgane vor uns. . . ." Mayser 

 and Emery consider the organs of the lateral line system to 

 form an accessory organ of hearing, whose function, even if not 

 strictly that of the perception of sound wave motion, neverthe- 

 less comes within the territory of the auditory function. 



Mayser found that the central terminations of the nerves 

 originating in these organs were intimately related to the 

 auditory centre in the medulla, and based his conclusions as 

 to their function mainly on this anatomical connection. 



We are thus enabled to understand how the organs of the 

 lateral line system, especially those in the head region, must 

 have a function analogous, if not identical, with that of the 

 auditory sense organs ; for they both take up vibrations from a 

 circumnatant liquid medium and transmit them to the nerve 

 ends, and both have, likewise, the same origin ontogenetically. 



While one set of organs has retained its primitive adult 



