IV ADVERTISEMENT. 



The Third Lecture was delivered May 14, 1874, by Dr. J. 

 M. Da Costa, on " Strain and Over-Action of the Keart." 

 Published by the Institution, August, 18T4. 32 pp. Svo. 



The Fourth Lecture was delivered January 20, 1875, by 

 Dr. Horatio C. Wood, on " A Study of the Nature and Me- 

 chanism of Fever." Published by the Institution, February, 

 1875, 48 pp. Svo. 



JOSEPH HENRY, 



Secretary Smithsonian Institution. 



Smithsonian Institution, 



Washington, January, 1877. 



