134 APPENDIX 



the saline bath, and the rod to which the preparation is tied, to be carried all of them by the 

 same vertical standard ; one adjustment to the recording-surface then moves them all. 



The rabbit is in my experience preferable to the cat, because in the former the beat of 

 the intestine and the contraction of the spleen and aorta are more readily and quickly 

 obtained. If a time-marker is used a suitable stroke is every tenth second. 



Obs. 1. Cat's intestine in my experience shows a slower rhythm than rabbit's. In 

 either case a duodenal piece beats quicker than an ileal. W. C. Alvarez states that the 

 beat-rate varies inversely as the distance from the pylorus {Amer. Jul. of Fhysiol. vol. 

 XXXV, p. 177, 1914). If the exercise is to be done at a class-meeting when at another table 

 the next following exercise is being done, the same carcase which furnishes the heart for 

 exerc. II can provide the intestine, spleen, and aorta for exerc. I. It is then preferable 

 for the heart preparation to be removed before taking the viscera for this exercise. The 

 rabbit is best killed as the gamekeeper kills it, by a quick blow behind the occiput. 



Kinger-Locke's fluid seems as serviceable for intestine as is Van Tyrode's, and has the 

 advantage that, being in use for other experiments, the preparation of a special saline for the 

 intestine experiment alone is avoided. The Einger-Locke for this experiment need not 

 have oxygen bubbling through it ; but it is well to blow air through it before use. For the 

 present exercise it need not have the dextrose recommended by Locke for perfusion of the 

 heart (see next exercise). The stock fluid keeps better without it. 



EXERCISE II 



For the graphic of this exercise and for some of those following the piece of travelling 

 paper required is longer than that sufficing for frog-muscle work. A suitable length to 

 allow at each place for such exercises is 120 cm. Such lengths are more conveniently not 

 kept cut, but are cut fresh from the stock-roll as wanted, with a straight-edge and sharp 

 knife. The cut should be truly at right angles to the paper-length, and so also the join of 

 the cut ends when gummed. If not fairly truly joined the paper will not run smoothly on 

 the drum, and as it travels will climb or sink, with liability to confuse the comparison of 

 pressure values, &c. 



For sooting^ the joined band supported by the two hands stretching it inside is moved 

 slowly over the sooting flame until there is sufficient deposit. When the soot-layer is 

 desired specially fine and uniform a good means is the following : The lamp of a small 

 paraffin cooking-stove with flat ribbon wick 10 cm. broad, set on a slate on the floor, is 

 covered by a .removable tall tin chimney also resting on the slate. The chimney — 60 cm. 

 tall, and of oblong cross-section with converging sides — has its two sides which are parallel 

 with the lamp-wick more convergent than the others, and these leave at top a slit-vent 

 26 cm, long parallel with the lamp-wick and something less than 1 cm. in breadth. A 

 side-opening with hinged lid low down in the chimney enables the hand to be passed through 

 to adjust the lamp-burner. The smoke issuing from the vent is of fine grain and evenly 

 distributed, and the paper passed over it runs no risk of scorching. Though the sooting is 

 rather slow the extra time is repaid where a trace may be intended for photographic reproduc- 

 tion or for mounting as a transparency (see below) for the projecting lantern. 



Fixing, The ordinary mastic varnish is excellent, but the fixative devised by Prof. 

 Stanley Kent has some advantages, especially for student records of over 1 m. length, as in 



