32 



A VERS. 



[Vol. VI. 



Man (Cut ii). 



In Man and other mammalia the utriculus^ forms a small 

 chamber, from which are given off seven processes. Five of 



these belong to the canals ; the other 

 two are the canalis reuniens and the 

 utricular blind sac. The utriculus 

 U and sacculus, although nearly equal 

 in size, are very small relative to the 

 long, enlarged cochlea, and they are 

 relatively of less importance than in 

 the Alligator. 



SACCULUS. 



The saccular regiofT of the Tor- 

 pedo, viewed from the side, is a 

 somewhat sickle -shaped body, with 

 the cutting edge of the sickle blade 

 directed forwards, downwards, out- 

 wards. The sacculus proper is a 

 broadly rounded sac with scarcely a 

 constriction where it opens into the 

 common utriculo- saccular chamber 

 above. The long axis of the sac 

 bends backwards and outwards from 

 the axis of the common chamber of 

 the ear, while its lagenar prolonga- 

 tion carries the axis forwards by a 

 bend at the point of origin from the 



Ctit II. — The left internal ear 

 of a human embryo, 22 mm. in 

 length, seen from without and be- 

 low. Figure after W. His, Jr. 

 The figure is from a model con- 

 structed from serial sections, and 

 represents the ear much magni- 

 fied, a, anterior canal; am, am- 

 pulla; am', amae (the middle 

 reference line is superfluous) ; 

 c, cochlea; d, ductus endolym- 

 phaticus; /;, external canal; j', sac- 

 culus (in the restricted sense ; 

 really only the recessus sacCuli) ; 

 u, utriculus. 



sacculus. The sacculus possesses 

 one of the canal sense organs, and its lagenar prolongation con- 

 tains a bud from this organ which in the higher forms grows 

 out into and forms the major portion of the cochlear organ. 

 The utriculo-saccular chamber of other vertebrates, as of the 

 forms described above, is really the transformed canal of the 

 primitive auditory organ, some of the offspring remaining in 

 the parental canal with parent organs just as the macula abortiva 



1 It should not be forgotten that the utriculus of these forms is really the primitive 

 utriculus plus a small portion of the primitive sacculus, i.e. that part of the chamber 

 from which the posterior canal arises is of saccular origin. 



