246 AVERS. [Vol. VI. 



the bony wall separating them. Search was made for some 

 means of arriving at the same goal experimentally. This patho- 

 logical condition suggested trying if increase of pressure in the 

 tympanic cavity would not produce the same symptoms as had 

 been observed in the two sets of cases detailed above. Salt 

 water of three-fourths per cent strength and varying in tempera- 

 ture from 9° to 15° C. was injected into the tympanic cavity and 

 produced with increase of pressure malposition of the head and 

 nystagmus. 



These symptoms continued to increase in intensity with the 

 increase in pressure. Most of the animals thus operated upon 

 recovered after unilateral injection ; the majority of those sub- 

 jected to bilateral injection usually died after a few days from 

 what the symptoms and post mortems proved to be inflamma- 

 tion of the brain. With water at 38° C. the pressure required 

 to produce these symptoms was greater than when colder water 

 was used, and most of the bilaterally injected animals lived, only 

 a few dying of inflammation of the brain. Other fluids were 

 used, e.g. concentrated salt solution, ammonia solutions, etc., 

 and they all produced the same symptoms, with rolling move- 

 ments. In these experiments the symptoms were the more 

 intense, the greater the chemical activity, and the greater the 

 pressure or the more rapid the injection. The death of the 

 animal operated upon usually followed in these cases on the same 

 or the following day, and post portem examination usually 

 showed hyperasmia or oedema of the brain, with inflammation or 

 hemorrhages of the parts of the brain subjacent to the ear. 

 These observations did not allow of any other interpretation 

 than that the fluids had penetrated to the brain, and the careful 

 examination showed that the membrana fenestrae rotunda was 

 always ruptured, allowing penetration of the liquids from this fo- 

 ramen through the perilymphatic spaces into the subdural space, 

 and from here on to the brain. As I have already shown, the 

 endolymphatic and perilymphatic spaces both communicate with 

 the cranial cavity, but in Munk's experiments the communication 

 was largely increased by rupture. Hydrostatic pressure obtained 

 by introducing a glass tube into the tympanic cavity and filling 

 it with water induced the same symptoms ; but if the symptoms 

 did not make their appearance after a certain pressure was 

 reached, they remained permanently absent. Wherever the 



