VF. 



ABC 



107 



strong, well-nourished cat the half-starved derelicts that some- 

 times find their way into a physiological laboratory have a dead 

 skin two or three days post-mortem. 



64. More A B C. Our second half-hour will have been 

 well employed if the application of what in the last lecture was 

 entitled the ABC method can be made absolutely plain. We 

 shall follow the system of notation that I then recommended to 

 your attention, and work through the four tests on a cat's foot in 

 accordance with the following diagram, which gives the ABC 

 switch in its several positions and the manner of its connection 



Co Che 

 keyboard. 



\\ 



Skin 



C A 



C A 



Excitation from B to A (B is anodic) 



Response outgoing at B 

 Excitation from A to B (B is kathodic) 



Response outgoing at B 

 Excitation from B to A (A is kathodic) 



Response outgoing at A 

 Excitation from A to B (A is anodic) 



Response outgoing at A 



FlG. 46. Cat's paw (24 hours post-mortem), A, B, C, as indicated above. Ex- 

 citation by tetanising currents. Berne coil. Two Leclanches. 10,000 units. The 

 response is always of the nature of an outgoing current at A, and at B for both direc- 

 tions of excitation. 



with the keyboard and galvanometer. You will see, if you trace 

 out the connections, that, with the switch in the first position, 

 deflection to your right means current from B to A, that in the 

 position II B it means current from B to C, and that in the posi- 

 tion II A it means current from C to A. By a glance at the 

 swatch and reverser, you can therefore recognise the direction of 

 excitation and the direction of response at B or at A ; and it 

 will be a perfectly simple matter to work through the four tests 



