MOIST CHAMBER. 163 



This is the arrangement adopted in the Physiological Depart- 

 ment of Owens College, so that a large number of men can work 

 at the same time, each being provided with recording apparatus 

 for himself. 



2. Cover the Cylinder with Paper. The paper is glazed on one 

 surface, and is cut to the necessary size to suit the drum. The 

 drum can be removed from the clock-work or other motor which 

 moves it, and is then covered with a strip of paper, the latter being 

 laid on evenly to avoid folds. One edge of the paper is gummed, 

 and slightly overlaps the other edge. Leave it for a few minutes 

 until the gum dries. The paper has then to be blackened, by 

 holding the drum and keeping it moving over a fan-tailed gas 

 burner, or paraffin lamp the former is preferable. Take 

 care that the soot from the flame is deposited evenly and 

 lightly, and see that it is not burned into the paper. The drum 

 is then placed in position in connection with its motor. 



3. General Rules to be observed with every Graphic or other 

 Experiment. 



(1.) In every experiment arrange the apparatus completely, 

 cover the drum with paper, and smoke it, before beginning 

 the dissection of the frog. 



(2.) See that the secondary circuit is " short-circuited." 



(3.) Test all the connections stage by stage as they are made. 



(4.) Each tracing is to be inscribed with the name of the 

 individual who made it, the date, and what it is intended to 

 show, and any other particulars it is desired to record. It is 

 then to be varnished, and the varnish allowed to dry. 



4. Myographs. Various forms are in use, but most of them 

 consist of a lever which is raised by the contracting muscle, and 

 so arranged as to record its movement on a smoked surface of 

 paper or glass. 



5. Moist Chamber (Fig. 61). To prevent a nerve-muscle pre- 

 paration from getting dry, it must be enclosed in a moist chamber, 

 which is merely a glass shade placed over the preparation, while 

 to keep the air and the preparation moist, the sides of the shade 

 are covered with blotting-paper moistened with water. 



