. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. POISONOUS SNAKES OF NOKTH AMERICA. 365 The external layer of the liuiiig of the i)it Leydig foiiud to be a coii- tinuatiou of the outer skin, Avhich, however, upon entering the cavity becomes thin and considerably modiiied. The granular tubercles grad- ually disappear toward the bottom, and the surface is found to be com- posed of large angular epidermis plates containing nuclei (fig. 10). Underneath this he found a layer of connective tiss
. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. POISONOUS SNAKES OF NOKTH AMERICA. 365 The external layer of the liuiiig of the i)it Leydig foiiud to be a coii- tinuatiou of the outer skin, Avhich, however, upon entering the cavity becomes thin and considerably modiiied. The granular tubercles grad- ually disappear toward the bottom, and the surface is found to be com- posed of large angular epidermis plates containing nuclei (fig. 10). Underneath this he found a layer of connective tissue, in which the fine ramifications of the thick nerve supplying the pit are lost in a granular substance which under high power reveals itself as containing numerous true, rounded, but pale nuclei. The granular substance he found arranged around the nuclei in such a way as to form groups or islands of various forms and sizes separated by light narrow spaces. These structures can only be regarded as terminal ganglions, and it does not seem doubtful that we have here to do with a true sense organ. v-s V, '/?/tii /;•/ ???f( /-,' ^. Fig. lU. PIECE OF SURFACE OF EPIDERMIS LIXINCi THE I'lT. Greatly enlarged, a Smooth, tliiu portion from the pit pi'oper; h tubercular )iiirti(in at the edge. (After Leydig.) Wherein this " sixth sense" consists we do not know, nor do we know of anything in the habits of these snakes which would indicate its nature, or to what use the animal puts the organ. Future research may reveal it, th(mgh ])erhaps man will never fully comprehend the nature of a sense which he himself does not possess. The "loreaF' pit, so called because of its location in that portiou of the snake's face in herpetological terminology known as the "lores," being a character exclusively ])ertaiuing to the Crotalid snakes, its pres- ence in any of our North American snakes at once designates it as a dangerously poisonous snake. It is an unfailing character
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