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Observations on the Labyrinth of Certain Animals. 



By Albert A. Gray, M.D., F.E.S.E., Aural Surgeon to the Victoria 



Infirmary, Glasgow. 



(Communicated by Professor John G. McKendrick, MJX, F.R.S. Received 

 January 26, — Read February 15, 1906.) 



[Plates 16—18.] 



The method of preparing the membranous labyrinth devised by the 

 writer* has made the study of that organ more easy. The difficulty which 

 previously attended the examination of the inner ear was so great that even 

 the extraordinary patience of Eetzius only permitted him to complete 

 the investigation of 5 mammals and 11 birds. In more recent times 

 Alexander has examined several more by the microscope, but the total 

 number altogether is still very small. 



The writer has already published the results of his investigations in the 

 seal and in man. The results of the examination of 14 other mammals are 

 at present in course of publication and will not be described in this paper, 

 except in so far as they throw light upon the subjects immediately under 

 discussion. It is necessary, however, to refer in general terms to the 

 anatomy of the inner ear in the case of the animals mentioned, in order that 

 that of those described in this paper may be properly understood. 



From an examination of 16 mammals the writer has found that the 

 different orders and species present differences in the anatomy of the inner 

 ear of three main types. These are (1) differences in the shape of the 

 cochlea ; (2) differences in the size of the perilymphatic space of the semi- 

 circular canals ; (3) differences in size of the otoliths. 



The cochlea appears in the mammals under two types in addition to the 

 peculiar type of the organ as found in the monotremes. These types are 

 the sharp-pointed cochlea which is found in the carnivora and the rodents, 

 and the flattened cochlea which is found in man, the monkeys, the lemurs, 

 the ungulates and the cetacea. In the case of the carnivora one exception 

 was found to this rule, the exception being the seal. This animal possesses a 

 cochlea which is rather bowl-shaped than pointed like those of the cat, dog, 

 and puma. There were no exceptions in the case of the ungulates, tbe least 

 flattened cochlea being possessed by the pig, but the difference between it and 



* ' Journal of Anat. and Physiology,' vol. 37, p. 379. 



