WITH THE MICROSCOPE. 99 



stop-cocks, and corks. One or two scalpels. Two or three pairs of 

 sharp scissars. Dissecting forceps. Bull's nose forceps. Curved needle 

 threaded with silk or thread, the thickness of the latter depending 

 upon the size of the vessel to be tied. Wash-bottle. Injecting fluid 

 in a small vessel. Plenty of warm water if the injection is to be 

 made with fluid containing size or gelatin. 



The student is recommended to practise the process by injecting 

 the organs and animals in the order in which they are enumerated, 

 and not to attempt the second until he has succeeded with the first. 

 In all cases the operation is to be conducted patiently, and very 

 slight pressure on the piston is to be exerted. 



1. Kidneys of sheep or pig. Artery. 



2. Eye of ox. Artery. Two or three minutes will be time enough 

 to make a complete injection. If the globe becomes very much 

 distended by the injecting process, an opening must be made in the 

 cornea which will permit the humours of the eye to escape, and 

 thus space will be left for the injection, and the vessels may be com- 

 pletely distended. 



3. Rat, mouse, frog. Injected from the aorta. 



4. Portion of intestine. Branch of artery. All divided vessels 

 being tied before commencing to inject, pi. XXV, fig. 164. 



5. Liver. In one part a branch of duct ; in a second, a branch of 

 artery ; in a third, portal vein ; and in a fourth, hepatic vein. The 

 portal and hepatic vein, the artery and portal or hepatic vein, or the 

 duct and portal vein may be injected with injections of different 

 colours in one piece of liver. 



Suppose the student is about to inject a frog. An incision is 

 made through the skin, and the sternum divided in the middle line 

 with a pair of strong scissars ; the two sides may easily be separated, 

 and the heart is exposed. Next the sac in which the heart is 

 contained (pericardium) is opened with scissars, and the fleshy 

 part of the heart seized with the forceps ; a small opening is made 

 near its lower part, and a considerable quantity of blood escapes 

 from the wound this is washed away carefully by the wash-bottle 

 p. 86. Into the opening 'the tip of the heart being still held firmly 

 by the forceps, a pipe is inserted and directed upwards towards 

 the base of the heart to the point where the artery is seen to be 

 connected with the muscular substance. Before the pipe is introduced, 

 however, a little of the injecting fluid is drawn up so as to Jill it, for if 

 this were not done, the air contained in the pipe would necessarily be 

 forced into vessels, and the injection would fail. The point of the 

 pipe can with very little difficulty be made to enter the artery. The 

 needle with the thread is next carried round the vessel, and the 



H 2 



