116 Mr. J. Blackwall on the meaiis by which various Animals 



of silver whenever its efficacy appeared to be diminished, and 

 after they had remained in it a sufficient time for the caustic to 

 act upon the pulvilli of the former and the tarsal brushes of the 

 latter, they were removed into the glass-jar, the vertical sides of 

 which they had previously ascended without difficulty. The re- 

 sult was precisely such as my former researches had led me to 

 anticipate ; the insects and spiders were rendered quite incapable 

 of walking on the sides of the jar, and the cauterized papilla3 

 connected with the inferior surface of the climbing apparatus 

 never again resumed their function ; yet by the help of their 

 claws the animals were enabled to ascend with ease the perpen- 

 dicular sides of objects having a slight degree of roughness. 



Satisfied that the cauterized state of the papillpe connected with 

 the climbing apparatus was attributable to the agency of the ni- 

 trate of silver operating through the medium of a fluid emitted 

 from their extremities, an experiment occurred to me, which, if 

 carefully conducted, promised to render the fluid apparent to the 

 eye when aided by a powerful magnifier. By subjecting the femur, 

 tibia and tarsus of the large flesh-fly and the common house-fly 

 to a moderate degree of pressure, a change was invariably per- 

 ceived to take place in the appearance of the extremities of the 

 hair-like papillae on the inferior siu'face of their pulvilli, which 

 assumed a silvery lustre, evidently occasioned by an increased 

 reflection of light. On passing a finger gently over the papillae 

 several times in succession, and again examining them under the 

 magnifier, the cause of the augmented brilliancy became obvious, 

 numerous granules of gelatinous matter being discovered upon 

 them, plainly consisting of the coagulated fluid emitted in minute 

 quantities from their extremities, and accumulated together into 

 particles of increased magnitude by the action of the finger, the 

 silvery lustre, at the same time, having disappeared. 



Thus it is clearly demonstrable that the papillae on the climb- 

 ing apparatus of two very common insects, remarkable for the 

 ao'ility of their movements on polished perpendicular surfaces, 

 emit from their extremities in exceedingly small quantities a fluid 

 coagulable on exposure to the atmosphere ; and this deduction 

 from direct experiment may be extended analogically to all those 

 insects and spiders which are capable of walking on the clean, 

 dry, vertical sides of polished bodies. 



To these recently ascertained facts I add a succinct review of 

 those previously recorded, which have exercised the most decided 

 influence in removing the difficulties which surrounded the subject 

 of this inquiry, in the hope that such an accumulation of valid 

 evidence, when fairly tested by others, will be considered as esta- 

 blishing the conclusion, that various animals, capable of walking 

 on the clean, dry surfaces of highly polished bodies in opposition 



