118 On the means by which Animals walk on polished Surfaces. 



sects, and the under side of the feet of the lar^se, which had their 

 efficiency speedily restored, however, on the removal of the im- 

 pediment by the customary process of cleaning the parts em- 

 ployed by each species. 



As a further confirmation of the accuracy of my opinion, I may 

 remark, that on careful and repeated examinations made with 

 lenses of moderately high magnifying powers, in a strong light 

 and at a favom-able angle, I never failed to discover \'isible tracks 

 left by spiders and insects in the larva and imago states when 

 moving in a vertical direction on clean glass. On submitting the 

 matter constituting the tracks to the direct rays of the sun in the 

 month of July, and to the action of brisk currents of air whose 

 drying power was great, I ascertained that it did not suffer any 

 perceptible diminution by evaporation under those circumstances ; 

 and it has been shown, in the recent experiments made by eni- 

 ploj-ing pulverized nitrate of silver instead of flom-, or chalk re- 

 duced to powder, and by inspecting under a powerful magnifier 

 the feet of flies when the superior joints of their legs were sub- 

 jected to moderate pressm'e, that a fluid, coagidable on exposm-e 

 to the atmosphere, is emitted in minute quantities from the pa- 

 pilla on the climbing apparatus of certain animals having the 

 power of walking on the vertical surfaces of highly polished 

 bodies. 



In my ' Researches in Zoology,^ p. 228, I have stated my con- 

 viction, founded on a minute inspection of specimens preserved 

 in spirit of wine, that tree-frogs, Hylce, and the lizards denomi- 

 nated Geckos, are enabled to move on the perpendicular sides of 

 polished objects by the agency of adhesive matter emitted from 

 papillae situated on the inferior surface of their toes ; those of the 

 former resemble the papillae on the pulnlli of the house-fly in 

 their distribution ; those of the latter being disposed in transverse 

 fasciae, somewhat in the manner of the papillae on the palate of 

 the cow, but vdi\\ less simplicity ; and whoever compares the two, 

 will be led, by analogy of structure and arrangement, to infer, 

 iipon physiological principles, that they perform a similar func- 

 tion, though from the different situations of the parts it cannot 

 be applicable to the same purpose. 



Such is the brief sm'vey which I proposed to give of the more 

 prominent facts elicited by my investigation of this interesting 

 subject. 



It is not at all surprising that a considerable degree of un\vill- 

 ingness should be felt to reject a generally-received opinion which 

 has long been regarded as established, or that a novel one sub- 

 stituted for it should be viewed with distrust or assailed with ob- 

 jections; but it certainly is extraordinary that the evidence by 

 which the one is corroborated and the other subverted should be 



