68 SURGICAL APPLIED ANATOMY. [Chap. v. 



sometimes occurred in connection with mischief in the 

 cells. The mastoid cavities, like the tympanum, con- 

 tain air, and in cases where the outer surface of the 

 bone has been spontaneously perforated, a tumour has 

 appeared on the skull that contained air, and that 

 could be increased in size by forcing air into the ear 

 through the Eustachian tube. Such tumours are 

 known as pneumatoceles, and the process that leads 

 originally to the perforation of the bone is of obscure 

 nature. In some cases it seems to have been simply 

 atrophic, and in other instances to have been due to 

 " caries sicca." 



On the anterior wall of the tympanum is the open- 

 ing of the Eustachian tube. This tube is one and 

 a half inches long, and by opening into the pharynx 

 serves to keep a proper supply of air in the tym- 

 panum, and so equalise the pressure upon the two 

 sides of the membrane. The pharyngeal orifice of the 

 tube is usually shut. During swallowing, however, it 

 is opened, by the action probably of the tensor palati 

 muscle. If the nose and mouth be closed, and the 

 cheeks blown out, a sense of pressure is produced in 

 both ears. The hearing, at the same time, is dulled, 

 and the change is due to the bulging out of the mem- 

 brana tympani by the air thus forced into the tym- 

 panum. This method of inflating the middle ear is 

 known as Yalsalva's method. 



In " Politzer's method " of passing air into the 

 Eustachian tube, the patient's mouth is closed, while 

 into one nostril the nozzle of a caoutchouc bag filled 

 with air is introduced, and the nostrils then held 

 firmly closed. The patient is asked to swallow a 

 mouthful of water, while at the same moment the bag 

 is forcibly emptied, and the air, having no other means 

 for escape, is thus driven into the open Eustachian 

 tube. The surgeon listens for the little noise caused 

 by the entrance of the air by means of a tube that 



