290 Intelligence and Miscellaneous Articles. 



meation or imbibition, very similar to what we have described 

 in the first. It is evident that if a substance were allowed to 

 remain permanently in contact with the nerve, the impressions 

 would be greatly defective, as the substances applied to it 

 would be mixed. To remedy this evil, it is requisite that a 

 means should be found of eliminating a substance from the 

 nervous extremities nearly as quickly as it is allowed to reach 

 them. The nerve when freed is capable of receiving a second 

 impression as clear and distinct as the first. We may easily 

 understand how this may be effected by means of the vascular 

 coil ; for if we suppose for a moment that this coil is filled 

 with stationary blood, we see no reason to prevent the diffu- 

 sion of the substance in the capillary area from taking place 

 in the same manner as in the cavity of the vesicle. If the 

 capillary is now emptied and filled with fresh blood, the same 

 action of imbibition and of solution will take place a second 

 time, and so on as fast as the blood is changed and renewed. 

 In this way we obtain a constant current from the exterior to 

 the interior of the vesicle ; and if the sapid substance h.as 

 quitted the surface of the tongue, the absorption will continue 

 until by an action of endosmosis and exosmosis it becomes 

 entirely removed from the vesicle. The existence of a constant 

 current in the coil undoubtedly much accelerates the removal 

 of the sapid substance from the vesicle, as we observe that 

 whenever an active imbibition takes place, as in the branchiae 

 of the tadpole, there exists a corresponding increase in the 

 vascular system. 



EXPLANATION 01^ PLATE IH. 



Fig. 1. Fungiform papilla with nerve ami blood-vessel. 



a. Nerve at the base of the papilla, where it forms an intricate 

 coil. Its tubules separate as they reach the internal convex 

 border of the [lapilla, where they form numerous convolutions in 

 the surface of the capillary. 



b. Afferent capillary. 



c. Efferent capillary. 



Fig. 2. Upper surface of the tongue of a young frog, with conical and 

 fungiform papilla;. 



'J'he papilla with the large dark area is a fungiform papilla in 

 its early stage of development. Above is another papilla of the 

 same kind, but more developed, with the central nucleus much 

 diminished. Around these are seen conical or tactile papillx. 



XLVII. Ititelligeiice and Miscellaneotis Articles. 



ON THE BEHAVIOUR OF METALLIC ZINC TOWARDS SOLUTIONS 



OF MERCURY. BY H. ROSE. 

 ri^HE behaviour of metallic zinc towards solutions of the peroxide 

 X and percliloride of mercury is highly remarkable. The zinc 



