AUDITORY TISSUES 21$ 



cut and laid on a slide, and xylol was used to remove the paraffin. The 

 dropping of a small amount of balsam was now enough to slightly 

 separate the cells, and this was further brought about by the placing of 

 the cover glass in position. If the displacement of the cells was too 

 great, a little collodion and clove-oil mixture was first placed on the glass, 

 and this served to retard the separation, which could also be controlled 

 in many other ways. The result is perfect in all ways but one ; i.e. the 

 tissue having been cut in sections makes it impossible to say if each cell 

 in the finished specimen is whole or not. 



LITERATURE 



OWSJANNIKOW TJND KOWALEVSKY. " Uber das Centralorgan und das Gehororgan der 

 Cephalopoden," Mem. d. I'Acad. de St. Petersburgh, T. XI. 



MORRILL, A. D. "The Innervation of the Auditory Epithelium of Mustellus canis," 

 Journ. of Morph., Vol. XIV, p. 6, pis. VII and VIII. 



PRENTISS, C. W. "The Otocyst of Decapod Crustacea," Bull. Mus. Comp. Zool., Har- 

 vard, Vol. XXXVI. 



THE TISSUES OF HEARING OR AUDITORY TISSUES 



These tissues are also modified forms of tactile tissues. They are 

 more delicate refinements, even, than the static tissues, since they per- 

 ceive and record the finest differences in the rhythm of successive impacts 

 caused by the waves of the atmosphere that are known as sound. 



The intermediate tissues in this case consist of two kinds. One 

 kind is intended to collect and thus intensify the sound and to convey 

 it to the auditory tissues which are usually very internal. These are 

 known as tympana and pinnae. A second kind are the delicate inter- 

 mediate structures that directly apply the sound waves to the auditory 

 nerve cells. These latter must be of exactly the right texture to properly 

 operate upon the delicate and highly specialized perceptory nerve-end- 

 ings, which here consist of various rods, hairs, or plates. In some forms, 

 these intermediate substances do not occur. Where they do occur, they 

 are special cell-products. 



In the vertebrates the auditory tissues are specializations of the 

 static tissues, and therefore the two are found to be closely related and 

 parts of the same organ. This is not the case in some of the insects 

 where there is a separate origin and position. 



For us to determine whether a given sense organ is auditory or static 

 in function is sometimes a difficult task, when we investigate such organs 

 as are other than our own. We must consider various points in this 

 connection. A comparison of the tissues of the mammals with our own, 

 structurally, tells us that most mammals must hear. It also tells us 



