CHAPTER XXVIII 



BRANCH CHORDATA (Continued^ CLASS MAM- 

 MALIA: THE MAMMALS 



THE MOUSE (Mas musculus) 



TECHNICAL NOTE. It is best to catch specimens alive in a good 

 trap. A live trap well baited and placed in some old granary 

 should furnish plenty for class use. White mice can often be ob- 

 tained at " bird-stores." When mice are not procurable, use rats. 

 A rat is perhaps preferable on account of its size, but all essential 

 structures can readily be made out in the mouse. Specimens 

 should be killed by chloroform as described for the toad, p. 5. 



Structure (fig. 147). Compare the external characters 

 of the mouse with those of the toad and sparrow. The 

 mouse, unlike the other vertebrates so far studied, is thickly 

 covered with hair all over its body except on the tip -of 

 the nose and the soles of the feet. Where are the nostrils 

 placed ? What are the large leaf-like expansions called 

 pinna situated just back of the eyes ? Pull open the 

 mouth and note the large incisor teeth on the upper and 

 lower jaw r s. Cut one corner of the mouth back and 

 observe the large flat-topped molar teeth on both jaws. 

 How does the attachment of the large fleshy tongue differ 

 from the condition in the toad ? The toad's tongue is for 

 snapping up insects, whereas in the mouse this organ 

 serves to move food about in the mouth. On the tongue 

 are numerous small taste-papilla. Notice the long hairs, 

 " feelers," on each side of the nose. Note the similarity 

 between the front paws and our own hands ; each has 

 four fingers with a small rudimentary thumb on the inner 



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