PRACTICAL CONDUCT OF EXERCISE I 



133 



plying two working-places. It is shiftable from one class-place to another as occasion requires. 

 It is obtainable from Mr. C. Nisbett, Thompson- Yates Laboratories, The University, Liverpool. 

 A suitable style for the writing-lever can be made with glass as follows : Glass tubing 

 drawn in the flame to fine capillary size for about 8 cm. length, and somewhat narrow er than 

 an ordinary vaccine tube, is bent over a small flame (a lighted match is enough) at right angles 

 about 1 cm. from one end and again about 5 cm. from the other, both bends being in the 

 same direction. The longer bent end is then bent again half-way down its length, this time 

 in a direction at right angles both to its own original direction and to that of the middle 

 stem whose two ends were bent before. The top of the end beyond the last-made bend is 



Text-fig. 43. Reducing gear clamp attached to vertical standard for table-bench. 

 P, the power-cord ; D, the distributing- cord moving eighty times more slowly than p. 



then fused to a tiny smooth knob. To fit this style to the straw recording-lever this latter 

 is for the greater extent of its length split lengthwise and one half of its resulting halves 

 cut away. But the straw is left tubular for its terminal 15 mm. or so ; this is then slit 

 along one side carefully, and the middle piece of the glass style is slipped through the slit, 

 so as to lie freely in the tubular collar which the straw forms for it. It then swings on an 

 axis pai^allel with the lever length, and its friction is minimal. This style rides easily over 

 the seam in the recording-paper, and writes well which of either ways the recording-surface 

 is travelling. It has long been a favourite in my laboratory for recording slow movements 

 such as are under observation in this exercise. The Bayliss writing-point (Stirling's Practical 

 Physiology, p. 376, 4th ed.) also answers excellently. It is convenient for the writing-lever, 



