INTRODUCTION 3 



when laid forward barely or not reaching eye ; tail shorter 

 than (rarely equal to) the length of head and body, darker 

 above than below; color of body normally grey-brown 

 above, white below; hind foot 38-46 millimeters" (Lantz). 

 The common albino rat {Miis n&rvegicus alhinus) is a 

 variety of the Norway rat, and is now known only as a 

 domesticated animal. Mus rattiis also has been known 

 to produce albinos. The large number of wild Norway 

 rats that can usually be caught in human communities, 

 together with the ease with which albinos can now be 

 secured from dealers, makes the Norway rat a convenient 

 form for laboratory study by large classes. Either the 

 wild Norway rat or its albino variety can be used for dis- 

 section in connection with the directions and descriptions 

 contained in this manual. 



