22 
Proceedings of the Royal Society of Edinburgh. [Sess. 
the bones of the head to the nerves in the labyrinth ; but that the waves, 
detached themselves from the bones and thus impressed the air contained in 
the tympanic cavity and in the sac-like projection of its membrane in the- 
baleen whales, and its prolongations into the accessory sinuses in the 
dolphins. The waves might then act in two ways, either through the 
fenestra ovalis and fenestra rotunda, by impressing the lymph in the 
divisions of the labyrinth and through it the end organs of the auditory 
nerve, or by setting in movement the chain of ossicles which have as 
their fixed point of attachment the malleo-tympanic interossification. 
Claudius, therefore, thought that the sound waves reached the head of 
a Cetacean through the water in which it lived ; that they were trans- 
mitted by the bones of the head to the air in the tympanic cavity, and 
that the waves generated in it directly caused vibrations through the 
fenestra ovalis and rotunda in the lymph in the labyrinth, as well as along 
the chain of bones, and impressed the nerve end organs. This view 
of the mode of excitation of the auditory nerve seems to be the most 
satisfactory. 
{Issued separately December 31 , 1913 .) 
