Mr, W oolhouse' s ReplT/ to Prof. Youno-, 209 



that if the thyro-arytenoidei are paralysed or their nerves di- 

 vided, the vocal chords will no longer vibrate. 



Although there is a great diversity of opinion respecting the 

 actions of the other muscles, they may nevertheless be easily 

 demonstrated on mechanical principles, vvhich has been partly 

 accomplished by Mr. Willis. 



In reference to their functions, the vocal organs may be re- 

 garded as a wind instrument, of which the lungs are the bel- 

 lows, the vocal tube the pipe, and the glottis, composed of 

 elastic vibrating membranes, is the reed. 



The type of these oi-gans is found in all the higher classes 

 of vertebrated animals, in mammalia, in birds, and in reptiles. 

 In fishes it may be considered as rudimental. 



The production of the most simple tone of voice requires 

 the associated actions of a most extensive range of organs *, 

 of which the following is a brief exposition. 



When the tension of the thyro-arytenoid ligaments takes 

 place they turn upon their axes ; their planes (which in a state 

 of relaxation are parallel t to the axis of the vocal tube) become 

 perpendicular J to it, and as the edges of the glottis approxi- 

 mate, its chink is closed up and acquires its true vibrating po- 

 sition J. 



[To be continued.] 



XLIII. Reply to Professor Young's concluding Remarks on the 

 TJieory of Vanishing Fractions. By W. S. B. Woolhouse.|| 



JN my last paper, on the theory of vanishing fractions, (p. 18,) 

 I have discussed the subject so fully and set forth so many 

 plain and straightforward mathematical arguments, completely 

 proving the truth of the general principles objected to by Pro- 

 fessor Young, that I conceive it would be quite superfluous to 

 make any further addition to what has been already so clearly 

 and satisfactorily established. 



Professor Young's concluding remarks on the theory of 

 vanishing fractions are, however, of so unrestrained and 

 extravagant a nature that I cannot possibly allow them to 

 pass without some notice. His observation that the expres- 



2 2 



sion - _ - implies an operation to be performed, and that 



• In the ordinary modulations of the voice more than one hundred mus- 

 cles are brought into action at the same time. 



t Fig. 4. 



t This state of the thyro arytenoid ligaments is the vocalizing position of 

 Mr. Willis: they will not however vibrate unless their edges ^through the 

 medium of the mucous membrane) be approximated, and when thus ad- 

 justed, they are in the state which I have denominated the true vibrating 

 position of the glottis. 



^ Fig. fi. II Communicated by the Author. 



Third Series. Vol.9. No. 53. Sept. 1830. 2 A 



