OHAPTEE XYI. 



EFFECTS AND USES OF SPIDER POISON. 



What are the effects of spider venom? Nothing connected with the 

 life history of spiders has given rise to greater diversity of opinion than 



this question. The well nigh universal belief is that all spiders 

 _ . . are very poisonous and their bite apt to be serious and even 



fatal to human beings. It is this, doubtless, which maintains 

 the most unjust popular dread of and hostility to these useful animals. 

 On the other hand, naturalists have been generally inclined to an opin- 

 ion quite the reverse of the popular one, and have held spiders as harm- 

 less to man. 



Let us first inquire what light anatomy can throw upon the subject. 

 More than two hundred years ago Leeuwenhoek gave a substantially cor- 

 rect description of the fang of a spider, pointing out the small aperture 



through which the liquid poison is emitted. 



Since that time the poison apparatus has 



been frequently described, and any 



one with a microscope can easily 



Indica- 



. , satisfy himself of the facts. What- 



Anatomy. -^ 



ever may be the effect of the secre- 

 tion from the poison glands of spiders, it is 

 certain that the organs and armature secret- 

 ing and conveying the venom are formida- 

 ble enough to suggest the idea of injury to 

 Fig. 241. View of the faices (fx) and fangs crcaturcs affcctcd thereby. The fangs of Ar- 



of Areriope cophinaria, from camera lu- . -, . . ■, • -rr\- n a -i -i 



cida drawing. The teeth on one side are glOp© COphuiaria are shoWU Ul Fig. 241, whcrC 



shown in outline, and the opening (o) in they are enlarged about fifteen times. The 



the fang is shown. X 15. i • i i f ^ • -i ,-i t • i 



mandibles from which the drawing was made 

 were taken from a nearly adult female. The falx, fx, was about two mil- 

 limetres long and one millimetre wide. The fang itself was about one 

 millimetre in length. When examined under the microscope it showed 

 very clearly the matrix in which the poison gland had been placed, as 

 seen in the outline drawing (camera lucida) at Fig. 242, g.m. One also 

 sees the canal, en, whicli contained the duct, and tlio little aperture at the 

 extremity, o, from whicli the secretion of the gland issued. 



(208) 



