130 Dr. Davy's observations on the 



venom-follicles are situated, and where there is a plexus of 

 veins of great size, as if intended for a reservoir of blood. 



This last-mentioned peculiarity of structure, and the situa- 

 tion of it, corresponding to the site of the gills of the tadpole, 

 would seem to indicate, that the sub-cutaneous distribution 

 of the second branch of the pulmonary artery, may aid the 

 lungs farther in their office by bringing the blood to the 

 surface to be acted on by atmospheric air. 



I have endeavoured to ascertain if there is any direct com- 

 munication by spiracula through the integuments. The 

 results I have obtained have been negative. I have intro- 

 duced air through a small incision, by means of a forcing 

 syringe, under the loose skin, also into the cavity of the 

 abdomen, and into the lungs by the superior glottis. The 

 air has been very much compressed under water, yet it has 

 been completely confined, not the smallest bubble having 

 been forced through the skin, or the lungs. 



When dried, the skin of the toad exhibits two kinds of 

 pores ; one kind, few in number, confined to the two tube- 

 rosities over the shoulders, sufficiently large to admit a hog's 

 bristle ; the other kind, very numerous, scattered over the 

 whole surface, and very minute. They are both of them 

 best seen by holding the skin between the eye and a strong 

 light; the smallest appears as luminous points of a yellow 

 hue ; the largest as indistinct circles. Both are covered 

 externally with transparent cuticle, and internally by a deli- 

 cate surface of cellular tissue ; some of the largest are also 

 covered with rete mucosum ; the smallest appears to be 

 destitute of this membrane. 



