S, S. MAXWELL 



353 



Careful dissection shows that mechanical relations analogous to 

 those just described hold also for the posterior ampulla and the hori- 

 zontal ampulla. 



I wish to point out the advantage which the vestibular mechanism 

 possesses on account of the mass of liquid. A relatively large free 

 mass of liquid with a relatively small surface would show more inertia 

 effect than a small mass with a relatively large surface area. 



This principle was shown in a model made by Mr. W. F. Hoyt. 

 Rossi^ had constructed a model of the size of a human semicircular 



Fig. 1. Diagram to show relation of vestibular structures to ampulla; v, vesti- 

 bule; u, utricle; ss, sinus superior; ac, anterior vertical canal; c, crista; n, nerve. 



canal and ampulla and reported that movement of the liquid in the 

 canal could be seen when the model was rotated. Hoyt made his 

 model of glass for the greater transparency, and filled it with a liquid 

 containing flakes of aluminium powder in suspension. When the 

 model was rotated very rapidly and then suddenly stopped he could 

 indeed see some movement in the canal, but the striking fact was 

 that a marked movement of rotation took place in the ampulla. 



® Rossi, G., Di un modello per studiare gli spostamenti della endolinfa nei 

 canali semicircolari. Arch. FisioL, 1914, xii, 349. 



