GENERAL CONSIDERATIONS. 21 



4. For determining the conditions of fatigue of muscles. 



5. For investigating the phenomena of the propagation of 

 impulses through the nerves, and of the excitement of 

 muscular action. 



6. For tracing and registering the rhythmic action of the 

 circulatory and respiratory operations cardiographs, 

 sphygmographs, stethoscopes, &c. 



7. Marey's apparatus for registering the paces of men, horses, 

 &c., and the actions of birds and insects during flight. 



S. Instruments for illuminating and rendering visible parts 

 within the living body ophthalmoscopes, laryngo- 

 scopes, &c. and arrangements for transmitting light 

 through parts of the living body. 



9. Instruments for varying the electrical state of the body 

 induction coils, &c. 



10, Instruments for determining the electric state of living 

 organs galvanometers with proper electrodes, elec- 

 trometers, &c. 



J. CLERK MAXWELL. 



