I 



ON MICROSCOPICAL EXAMINATION. XXV 



over which is a water-tap with a foot or two of wide india- 

 rubber tubing attached. 



When everything is ready, kill the animal, and as soon as 

 it is dead, lay it open, cutting as few blood-vessels as possible. 

 Expose the root of the aorta or other vessel from which it is 

 intended to inject the animal ; choose a cannula of the right 

 size ; fit it with an india-rubber connection ; fill it with salt- 

 solution, and stop the end of the connection with a glass plug. 

 Pass a ligature round the vessel ; make a longitudinal slit in 

 the vessel ; insert the cannula ; tighten the ligature upon it, 

 and tie it with a bow. If the ligature be too tight it will 

 cut the vessel. Fill the syringe with the warm salt-solution ; 

 remove the plug from the cannula ; press the body of the 

 animal slightly, to remove some of the blood from its vessels, 

 and to get rid of any clot that may have formed close to the 

 cannula. Inject the salt-solution, to force the remaining 

 blood from the vessels before it can coagulate ; and wash or 

 sponge the blood away. If the arteries are being injected, 

 the vena cava and portal veins should be cut open to allow 

 free escape of the blood, and vice versa. 



Mix the plaster of Paris in the mortar, stirring in the 

 colour, and making the plaster thin. Strain it rapidly through 

 the muslin, and inject immediately with the syringe. When 

 the vessels appear to be well injected, remove the syringe 

 and insert the glass plug, and wash the animal to get rid of 

 blood and any injection that may have escaped. 



Allow the animal to remain two or three hours in cold 

 water before dissecting it or putting it into spirit. 



VI. ON MICROSCOPICAL EXAMINATION. 



The microscope affords the means of investigating the 

 structure of minute animals, and the finer details of those 

 of larger size. The microscopical examination of the special 

 organs of the larger animals is of great importance, and must 

 on no account be neglected. 



The microscope consists of a body and a stand. The body 



