221 



labyrinth, protects the ear from the injurious influence of very, 

 powerful vibrations. 



3. The stapedius muscle, by slightly relaxing the memhrana 

 tympani and the fluid of the labyrinth, places the ear in a position 

 to be influenced by vibrations of a most delicate character. 



4. Another function of the memhrana tympani is to form part of 

 the resonant walls of the closed tympanic cavity. 



5. The guttural orifices of the Eustachian tubes are closed, and the 

 tympanic cavities do not communicate w^th the cavity of the fauces 

 excepting during certain muscular actions. 



6. In man and some mammalia the Eustachian tubes are opened 

 by the muscles of the palate, in other animals by the superior con- 

 strictor of the pharynx. 



7. In birds there is a membranous tube common to the two 

 osseous Eustachian tubes, and this common tube is opened by the 

 action of the internal pterygoid muscles. 



8. For the function of hearing to be perfect, it is requisite that 

 the tympanic cavity should be closed from the outer air. 



3. *' An Experimental Inquiry undertaken with the view of ascer- 

 taining whether any, and what signs of current Force are mani- 

 fested during the organic process of Secretion in living animals " 

 (continued). By H. F. Baxter, Esq. Communicated by R. B. Todd, 

 M. D., F.R.S. &c. Received April 30, 1852. 



The present communication is a continuation of a series of expe- 

 riments, the first part of which was published in the Phil. Trans, 

 for the year 1848. The object is to show that the changes which 

 occur during the organic process of secretion in living animals are 

 accompanied with the manifestation of current force ; and the prin- 

 cipal facts upon which this conclusion is founded are the following :— 



1st. It was found that when the electrodes of a galvanometer are 

 brought into contact with the secreted product and the venous blood 

 flowing from the same organ, an eff^ect upon the needle is produced, 

 indicating the venous blood to be positive. This fact was established 

 in the liver, kidneys and mammary gland. 



2ndly. The eflfect could not be referred to the heterogeneity of the 

 fluids without assuming that the blood was acid and combined with 

 the secreted product ; nor could it be referred entirely to thermo- 

 electric eff'ects, inasmuch as the current varied in each organ, and 

 was capable of traversing a liquid conductor. The effects, however, 

 may be partly due to catalytic actions on the combining power of pla- 

 tinum ; and this last supposition tended to confirm the opinion ori- 

 ginally entertained by Wollaston, that the changes which occur 

 during secretion are analogous to those which take place in the de- 

 composing cell of a voltaic circle. 



Without giving any definite opinion as to the lungs performing 

 the ofiice of a secreting organ, it was found, that when one electrode 

 was in contact with the mucous surface, and the other in contact 

 with the blood in the pulmonary veins, an eff'ect occurred upon the 

 needle indicating the blood (arterial) to be positive. This fact ap- 



