88 SPIDERS [CH. 



a single small blade, rather more than half open 

 when in use, closed when at rest. The handle of the 

 penknife is certainly in most cases very short and 

 thick, and the blade not really a blade at all, for 

 it has no cutting edge, but is a "fang" or piercing 

 instrument generally somewhat curved, and with 

 a sharp point. The " blade ' is, moreover, perforated 

 by a tube which comes from the poison-gland, situated 

 in the thickened " handle," or in the spider's head, so 

 that poison can be forced into the wound which it 

 inflicts. 



Now take two penknives with the blades half open 

 and hold them so that they hang with the hinge 

 downward and with the blades directed towards each 

 other ; it is clear that the blades may be made to 

 pierce an object situated between them by moving 

 the handles laterally, the object being attacked 

 simultaneously on either side. This is the arrange- 

 ment in the true spiders, whose jaws move sideways, 

 though they do not always hang perpendicularly, 

 but are more often somewhat slanted forwards. 



To represent the jaws of a theraphosid spider the 

 penknives must be arranged differently. Place the 

 handles horizontally and parallel to each other, with 

 the blades directed downwards and also parallel. 

 They will now work not sideways, but up and down, 

 and both fangs will pierce the victim from above. In 

 a word, the true spiders have jaws which can be 



