CONTENTS. 



XIX. Consideration of the objections raised against the geometrical representa- 

 tion of the square roots of negative quantities. By the Rev. John 

 Warren, M.A. of Jesus College, Cambridge. Communicated by Thomas 

 YouNGj M.D. Foreign Secretary to the Royal Society. . . page 241 



XX. Anatomical description of the foot of a Chinese female. By Bransby 



Blake Cooper, Esq., Surgeon to Guys Hospital. Communicated by 

 Peter Mark Roget, M.D., Secretary to the Royal Society. . . 255 



XXI. Some observations on the functions of the nervous system, and the relation 

 which they bear to the other vital functions. By Alexander Philip 

 Wilson Philip, M.D. F.R.S. L. 8s E 261 



XXII. On the respiration of birds. By William Allen and William Hasle- 

 DiNE Pepys, Esqrs. Fellows of the Royal Society 279 



XXIII. On the spontaneous purification of Thames water. By John Bostock, 

 M.D. F.R.S. S^c 287 



XXIV. On the composition of chloride of barium. By Dr. Edward Turner, 

 Professor of Chemistry in the University of London. Communicated by 

 Dr. DioNYSws hAHDN^R, Fellow of the Royal Society 291 



XXV. On a new series of periodical colours produced by the grooved surfaces 

 of metallic and transparent bodies. By David Brewster, L.L.D. F.R.S. 

 L.8sE. 301 



XXVI. On the Nerves of the Face ; being a second paper on that subject. By 

 Charles Bell, Esq. Fellow of the Royal Society 317 



