252 EXPERIMENTAL INVESTIGATION OF THE ACTION OF MEDICINES. 



generally restrict this process to evaporating the urine, or 

 testing it either chemically or by injecting some of the extract 

 into another animal. 



Mode of Securing Animals. — In order to determine in an 

 exact manner wliat organs or parts are affected, we are obliged 

 to make nse of apparatus of various kinds ; and, before these 

 (an be applied to an animal, it musfc be prevented from moving. 

 Frogs are fastened to a frog-board by a piece of cord with a 

 noose at the end, slipped over each elbow and ankle. The frog- 

 board may consist of a piece of mill-board about 9 inches long by 

 3 inches broad, with four slits at the sides to keep the cords in 

 position, or of a piece of wood the same size, and from a quarter 

 to half an inch thick, with holes, through which the cords are 

 passed. They may be fastened by simply tying them together 

 or by sticking a small wooden pin into each hole, or by four 

 screws, such as are used by fastening the wires of galvanic 

 batteries, placed in the edges of the board. The last way is, I 

 think, the most convenient. Eabbits are best secured by 

 Czermak's holder and board (shown in Fig. 126). The best cord 

 is strong window-cord. The one end should be flattened with a 

 hammer, and turned over so as to make a small loop, whose 

 two sides are then firndy bound together with waxed thread. 

 Through this loop the other end is passed, and the noose thus 

 made is ready to be drawn tight at any moment. The other 

 end of the cord should be cut to a point and also bound with 

 waxed thread to prevent the strands unravelling. The rabbit is 

 placed on the board, the nooses slipped over the legs and drawn 

 tight, and the ends of each cord passed through the screw which 

 will be nearest it when the animal lies on its back. The rabbit 

 is then turned over, and the cords drawn through the screws 

 and fastened. The bar h is then put between its teetli, and the 

 screw I turned till g and g' fit tightly over its muzzle, and the 

 projecting ends of g fixed into the ends of / Dogs may be 

 fastened by Bernard's holder (Fig. 127a), or by a simple bar of 

 iron put behind their canine teeth. A piece of cord is first tied 

 round the upper jaw, the bar put into the mouth, and the two 

 jaws tied firmly over it. A split trap may be used instead of 

 the cord. I have had a bar made with a hole at each end, into 



