Contributions to Physiological Technique 



371 



When, therefore, the key is in the position shown in fig. 8, A is shut ofi", 

 while B is connected to C. If the key be now turned clockwise through 

 90°, B will still be connected with C by virtue of half of the one transverse 

 channel, and the prolongation of C upwards and forwards, but A will be put 

 in connection with the bye-pass D, the hitherto unemployed perfusion-fluid 

 now running to waste. Another turn clockwise through 90° shuts off B 

 from C, but connects A with it instead of with the bye-pass, a change fi-om 

 one perfusion-fluid to the other being now effected. Another turn clock- 



Fio. 8. — For description see text. The Greiner and Friedrichs oblique 

 key-borings are indicated by light dotted lines. The special additional 

 passages are shown dark. The stopcock was filled with dark fluid 

 before being photographed. 



wise through 90° leaves A still in connection with C, but connects B with 

 D, the perfusion-fluid first employed now running to waste. Another turn 

 clockwise through 90° restores the state of affairs shown in fig. 8, changing 

 the perfusion-fluid to the one in use at the start. 



Midway between the second and third, and also between the third and 

 fourth (first), of the positions of the key just described, A and B are com- 

 pletely shut off from C and D, all perfusion being cut off, with no perfusion- 

 fluid running to waste. 



Spots of different coloured enamel are fused on the ends of the key- 



VOL. I., NO. 4. — 1908. 25 



