36 MR. J. BLACKWALL ON THE POISON OF 



These experiments do not present any facts which appear to sanction the opinion that 

 insects are deprived of life with much greater celerity when pierced by the fangs of spiders 

 than when lacerated mechanically to an equal extent by other means, regard being had in 

 both cases to the vitality of the part injured, as the speed with which existence terminates 

 mainly depends upon that circumstance. It is true that the catastrophe is greatly acce- 

 lerated if spiders maintain a protracted hold of their victims, but this result is obviously 

 attributable to the extraction of their fluids, which are transferred by oft-repeated acts of 

 deglutition into the stomachs of their adversaries. 



From the entire mass of evidence supplied by the experiments taken in the aggregate, 

 it may be fairly inferred that whatever properties characterize the fluid emitted from the 

 orifice in the fangs of the Araneidea, it does not possess that degree of virulence which is 

 commonly ascribed to it, neither is it so destructive to animal life when transmitted into 

 a recent wound as it is generally supposed to be. "Were I disposed to speculate upon the 

 manner in which it affects insects on being introduced by the fangs into their vascular 

 system, I might conjecture that it has a tendency to paralyse their organs of voluntary 

 motion, and to induce a determination of their fluids to the part injured ; but I refrain 

 from dwelling upon a suggestion, however plausible it may appear to be, which in the 

 present state of our knowledge of the subject can only be regarded as hypothetical. 



4. Experiments on Inanimate Substances. 



In the month of September 1846, litmus paper presented to spiders belonging to several 

 genera when in a state of extreme irritation, having their fangs extended, and the trans- 

 parent fluid which issues from the fissure near their extremity conspicuously accumulated 

 there, on being seized invariably became red as far as the fluid spread round the punctures 

 made in it, a result clearly proving that this animal secretion, though tasteless, is an acid. 

 Care, however, must be taken, in conducting the experiment, not to suffer any fluid from 

 the mouth to blend with that which proceeds from the fangs, either before or after it has 

 been transferred to the litmus paper, the former, rendering the blue colour of the test 

 more intense, and restoring it after it has been converted to red by the action of acetous 

 acid, being decidedly an alkali ; consequently, if both combined in due proportions, they 

 would neutralize each other ; but as there is usually a much more copious supply of the 

 alkaline than of the acid fluid, its agency would predominate, and scarcely a trace of red 

 would be discerned on the litmus paper. 



Submitted to the same chemical tests, the fluid contained in the stomachs of spiders 

 and that which flows from wounds inflicted on their bodies and limbs were found to be 

 alkaline. Now if the frequency and suddenness with which large quantities of fluid are 

 propelled into the mouths of spiders when occupied in extracting nutriment from their 

 prey be borne in mind, the conclusion that they must be ejected from the stomach through 

 the narrow oesophagus and pharynx seems to be inevitable*, as there is not any other 



* The statement of Savigny, that some spiders have three pharyngeal apertures, does not appear to he applicable 

 to several of our larger indigenous species, as I have not been able to detect more than one such aperture in Cinifio 

 ferox, Ccelotes saxatilis, Tegenaria civilis, Agelena lahyrinthica and Ep'eira quadrata, on the most careful inspection. 



