EAT: LABORATORY WORK. 



If possible, the student should be provided with two 

 specimens, one injected, the other not. If rats are not 

 easily obtained, a single injected specimen will suffice. Rats 

 may be injected by cutting into the left ventricle and in- 

 serting the canula into the aorta from this opening, ligating 

 it by tying in front of the heart. A gelatine mass works 

 best, but care must be taken lest the delicate vessels be 

 broken. Only a small amount of fluid is necessary to fill 

 all the vessels. 



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 i* Sketch 

 the sole, bringing out the callous spots. How many toes 

 in the hind-foot ? Sketch the sole and compare 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 

 third eyelid at inner angle of the eye. Does it resemble any 

 structure you have found in the animals previously studied ? 

 Is there anything similar in your own eye ? 



86 



