THE UTRICLE AND SACCULE. 1167 



utricle and saccule. The most primitive form of internal ear is un- 

 doubtedly a sac containing fluid in which an otolithic mass is immersed, 

 and having on the wall hair-like processes related to the terminations of 

 a nerve (Aurelia aurita, Unio, Phialidium, Pterotrachea). Such an 

 arrangement is adapted to receive impulses from the surrounding 

 water. 1 In the lower vertebrates we find a single sac, into which open 

 the semicircular canals ; still higher we find the beginning of the ductus 

 cochlearis ; and, lastly, a division of the single sac into two, with a great 

 development of the ductus cochlearis. These facts point to the sacs 

 being organs for the reception of waves giving rise to sensations of 

 sound as sound, and without reference to pitch or quality. Animals 

 furnished with internal ears in which the cochlea is absent or only 

 developed to a slight extent, no doubt have sensations that correspond 

 to tones and noises, but these would differ only as regards intensity. 

 Such sensations would be similar to visual sensations of luminosity, 

 without reference to colour. To analyse auditory sensations, a more 

 complicated mechanism is necessary, and hence we find the gradual 

 evolution of a cochlea. 



In man and the higher animals there can be no appreciation of sound 

 irrespective of pitch and quality, because the movements of the stapes 

 will not only call into action the nerve-endings in the utricle and saccule, 

 but also those in the cochlea. One cannot conceive the vestibular 

 portion of the internal ear acting alone. As, however, the two sacs are 

 each supplied by a special nerve, it is not improbable that movements 

 of the base of the stapes acting on both may give rise to two dis- 

 tinct effects, but there is no experimental evidence bearing upon this 

 point. 



When we take into account the minute size of the parts, and their 

 situation in the temporal bone, the results of direct experiments on the 

 ear of a living animal must be received with caution. Still the evidence, 

 meagre as it is, is in favour of the view above set forth. Thus, Flourens 

 destroyed all the nervous filaments to the labyrinth except those supply- 

 ing the saccule and utricle, without observing deafness. Others have 

 observed disease of the cochlea causing its destruction, but without 

 complete loss of hearing. 2 Destruction of the semicircular canals does 

 not cause deafness. Gelle states that after he destroyed the cochlea 

 in guinea-pigs, deafness came on only after inflammatory changes had 

 invaded the structures in the vestibule. 3 



Eecently Lee 4 has argued that as fishes have no papilla acustica basilaris, 

 and as, with few exceptions, they are dumb, it is highly probable they have 

 no sense of hearing. Actual experiment appears to support this contention. 

 The papilla acustica basilaris appears first in amphibia in an offshoot from the 

 lagena, and, in the higher animals, it becomes part of the organ of Corti. If 

 this view be correct, then the cristae and maculae acusticse have nothing to do 

 with hearing, but serve for the perception of movements, such as those of 

 rotation and translation through space, which are infinitely coarser than those 

 which are the physical basis of sound. Lee has also endeavoured to show 

 that the organs in the lateral line of fishes and the maculae and cristse acusticae 



1 For an excellent account of the comparative anatomy of the internal ear, see article 

 ;< Audition," by Gelle", in Richet's "Diet, de physiol.," tome i. pp. 914-919. Figures 

 showing the internal ears of these animals are given in this article. 



2 Valsalva, Moos and Steinbrugge, Ztschr. f. Ohrenh., Wiesbaden, tome xi. p. 281. 



3 "Fonctions du lima^on," Etudes d'otologie, 1880, tome i. 



4 Am. Journ. Physiol., Boston, 1898, vol. i. p. 128. 



