RAT. 



If possible each student should be provided with two speci- 

 mens, one injected, the other not. If rats are not easily ob- 

 tained,, a single injected specimen will suffice. The injection 

 is easiest made by removing the skin on the inner side of the 

 thigh, exposing the femoral artery and vein. The canula can 

 be inserted in these, pointing towards the head, and the whole 

 of both arterial and venous systems filled. Only a small amount 

 of injecting fluid is necessary, and care should be taken not to 

 break any of the vessels by too great pressure. For the study 

 of the heart and brain it is well to provide each student with 

 these parts from some larger animal like a sheep, hardening 

 and preparing them some time before they are to be used. 



EXTERNAL. 



With what is the body covered? Is there hair on the 

 tail? Do you find scales on the tail? In what respect 

 do they resemble and in what differ from those of reptile 

 or fish? 



How many toes on the fore feet? Do you find any 

 trace of a thumb? Are the toes provided with claws? 

 Sketch the sole, bringing out the callous spots. How 

 many toes in the hind foot? Sketch the sole and com- 

 pare with that of fore foot. 



How many nostrils ? Of what use to the animal are the 



*/ 



'whiskers' of the upper lip? Examine eyes and look for 



53 



