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V. Experiments and Observations on the Poison of Animals of the Order Araneidea. 



By John Blackwall, Esq., F.L.S. 8fc. 



Read December 19, 1848. 



M.UCH has been written about the deleterious property of the transparent colourless 

 fluid emitted from the minute orifice situated near the extremity of the fangs of spiders 

 on the side next to the mouth, when those instruments are employed to inflict a wound. 

 The numerous accounts which have been published by various authors of the singular 

 effects induced in the human species by the bite of the Tarantula {Lycosa tarantula apu- 

 liw, Walck.), and of the still more extraordinary mode of cure, together with the serious 

 and sometimes fatal consequences which have been attributed to the bite of the Malmig- 

 natte {Latrodectus malmignatus, Walck.), must be regarded as amusing fictions in the 

 natural history of the Araneidea ; and if the opinion, prevalent among arachnologists of 

 the present day, that insects pierced by the fangs of spiders die almost instantaneously, 

 should be found on examination to be at variance with well-ascertained facts, it must in 

 like manner be deemed fanciful. 



For the purpose of testing the validity of this opinion, which I had reason to doubt, 

 and in order to determine with a nearer approximation to accuracy than had previously 

 been done, some of the effects produced under divers circumstances by the poison of spiders, 

 more especially the degree of influence it exercises in destroying the vital functions of ani- 

 mals, in the summer of 1846 I commenced an experimental investigation of the subject, 

 the particulars of which are comprised in the following pages. 



To avoid confusion, the experiments have been arranged under four distinct heads, 

 corresponding to the objects upon which they were made; namely, the human species, 

 spiders, insects, and inanimate substances. It may be proper to premise that all the 

 animals were adult individuals in vigorous health, and that the temperature of the atmo- 

 sphere, in every instance recorded, was ascertained by means of a thermometer graduated 

 according to Fahrenheit's scale, and exposed to the open air in a shady situation having a 

 northern aspect. 



1. Experiments on the Human Species. 



On the 19th of July 1846, a female Epeira diadema was induced to bite me on the inner 

 side of the left hand, near the base of the forefinger ; it continued to force its fangs deeper 

 into the flesh during a period of many seconds, and at last quitted its hold voluntarily, 

 when a little blood issued from the wounds it had inflicted. Though the spider was in a 

 state of great excitement from previous irritation, yet I did not experience more inconve- 

 nience from its bite than from a puncture made near it at the same time with a fine 

 needle ; indeed, allowing for a considerable degree of compression in the former case, the 

 effects of both injuries appeared to be very similar. The thermometer, while the experi- 



