2 IRVING HARDESTY 



comparing the fresh with teased out membranes acted upon bj' 

 various fixing fluids, and by experimenting with methods of 

 embedding for sections of the cochlea in which more normal 

 appearances of the membrane might be retained. Cochleae 

 of pigs were used wholly in that investigation, almost entirel> 

 from pigs at or near 'term.' Those of one young suckling pig 

 were obtained. The paper made no attempt to cover the proc- 

 ess of the development of the tectorial membrane further than 

 to give a brief review of the various publications bearing upon 

 it and then considered as already having well covered the proc- 

 ess, and it gave one drawing showing one stage of the develop- 

 ment for use in describing the assumed process by which its 

 final structure is acquired and its adult position with reference 

 to the spiral organ is attained. 



Since the publication of the above paper dealing with the mem- 

 brane in young animals, the writer has been occupied in an at- 

 tempt to construct a model of the auditory apparatus in which 

 the proportions, position and environment of the tectorial 

 membrane in the cochlea are simulated and by which its behavior 

 when subjected to the energy imparted to it by sound waves 

 may be illustrated. In the construction of this model, a fur- 

 ther detailed stud}^ of the proportions and position of the actual 

 tectorial membrane seemed necessary, and in this study it be- 

 came evident that the observations should be carried to the 

 membranes of adult animals rather than confined to those in 

 the cochleae of embryos and fetuses. Since several of the re- 

 sults of this further study seem of interest, though some of them 

 are confirmatory^ of results previously published, and since 

 relatively so few observations upon the adult mammalian cochlea 

 have been recorded, it is the purpose of the present paper to 

 give certain of the findings of a somewhat detailed study of the 

 spiral organ of the adult mammal. The shape, proportions, 

 position and attachment of its tectorial membrane are especialh^ 

 considered. Toward the end of the study, certain points in the 

 question of the attachment and position of the adult membrane 

 and the structure of its surfaces arose in comparing the findings 

 with those recorded for the membranes in cochleae of embrvos 



