A New Ganglion in the Human Temporal Bone. 323 



A modification of the interpretation on these lines, however, does not affect 

 the general hypothesis as to the existence of several types of white flowers, 

 or the inference that pigment is not necessarily produced although all the 

 requisite ingredients for the production of colour may be present. 



On the Occurrence of a Ganglion in the Human Temporal Bone 



not hitherto Described. 

 By Albert A. Gray. 



(Communicated by Prof. J. G. McKendrick, F.R.S. Received November 26, 1912, 



—Read February 6, 1913.) 



(Plate 6.) 



The existence of a previously unknown nerve plexus associated with a 

 comparatively large ganglion embedded in the substance of the human 

 temporal bone must be regarded as a somewhat surprising fact at this 

 period in the history of human anatomy. It may be well, therefore, to 

 describe in a few lines the process which led to the discovery. 



While making some preparations of the middle ear of animals according 

 to my own method, I discovered the presence of a large plexus of nerves 

 on the posterior surface of the bulla of the sheep. This plexus was found 

 to be composed of bundles derived from the pneumo-gastric and the 

 facial nerves. Since the preparation was only macroscopic, I was unable 

 to ascertain whether nerve ganglion cells were present. Such a plexus 

 has not been described in the human subject, unless the two minute 

 bundles of fibres which pass between Arnold's nerve and the facial nerve 

 be dignified by the name of plexus. It seemed, therefore, highly probable 

 to me that some corresponding structure might exist in the human subject 

 which had not hitherto been described, and a search was accordingly made. 



The initial difficulty lay in the fact that this portion of the temporal bone 

 is very different in man from that in the sheep. In the latter there is 

 a large bulla, but no mastoid process ; whereas in man there is a large 

 mastoid process and no bulla. In man the only indication of a bulla is 

 the little cul-de-sac which runs backwards from the lower, inner, and 

 posterior corner of the tympanum. In the human subject a mass of bone 

 fills the space which in mammals is occupied by the bulla. The plexus, 



