FOKM AND FUNCTION 



251 



apt student takes up the study of the skeleton of the 

 grasshopper he will readily see that its skeleton serves 

 identically the same purpose as the human skeleton. 

 The integral parts of the human skeleton we call bones; 

 the separate portions of the insect skeleton we term 

 sclerites. That constituent which gives bones their firm- 

 ness we commonly speak of as lime; that which lends 

 rigor to the sclerite is called cliitine. 



An examination of the body-wall of an insect shows it 

 to be composed of a number of distinct pieces or sclerites. 

 The lines separating these pieces are known as sutures. 

 Sutures here, just as in the anatomy of the human skele- 

 ton, are not freely movable joints. That term is re- 

 served for those articulations which are freely movable ; 

 for example, joints of the locust's leg. 



FIG. 191. Plan for simple microscope stand. 



Aids in the Laboratory. In addition to the appliances, 

 net and lens, already mentioned, the following simply 

 constructed materials will be of assistance : 



It will at times be found advantageous to have the 

 specimens stationary, in order that the parts being stud- 

 ied can be manipulated under the lens. For this pur- 

 pose, Figure 191 shows a simple dissecting microscope 

 stand, made from a 4 x 4-inch pine block nine inches 



