96 GENERAL PROPERTIES OF LIVING TISSUES 



the margin a shallow groove. In this groove rests a 

 glass cover which for the sake of clearness has been 

 omitted from the figure. To the porcelain plate is 

 screwed a rod, by which the plate may be supported 

 on a stand. Within the glass cover are two right- 

 angled rods. One of the rods carries a small clamp, 

 composed of a split screw on which moves a nut, by 

 means of which the femur of a nerve-muscle prepara- 

 tion may be firmly grasped. The holder for the split 

 screw is arranged to permit of motion in all directions. 

 Both right-angled rods carry uupolarizable electrodes. 

 Each of these is borne by a hard-rubber holder. By 

 turning the leg of the boot in the holder the foot may 

 be brought as near the foot of the neighboring elec- 

 trode as may be desired. It is desirable to mount 

 the boots on opposite rods as in Fig. 24. A thick 

 wire of freshly amalgamated zinc, provided at one 

 end with a hole in which a connecting wire may be 

 fastened with a set screw, is placed in the leg of the 

 boot, and the other end of the connecting wire 

 brought to one of the four binding posts shown in 

 Fig. 24. These four posts are in electrical connec- 

 tion with four other posts beneath the porcelain 

 plate. The air within the moist chamber may be 

 kept saturated with water vapor by applying moist 

 filter paper to the inner side of the glass globe. 



Destruction of the Brain by Pithing. The 

 next experiment requires a curarized muscle, and 



