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Show 1890.] HELODERMA SUSPECTUM. 207 the outer surface of the mandible, where they entered. Fischer found in his specimen that these ducts branched as they quit the gland; this was not the case in the reptile examined by me. Each duct passes obliquely upwards and inwards through the lower jaw, and its internal opening within the mouth is found at the base of the tooth it supplies, near the termination of the groove of the tooth. These glands resemble each other in size, shape, and position, and they in all probability have the same function. Either one of them lacks something of being rather less than two centimetres for its antero-posterior diameter, and is about a centimetre wide. Subelliptical in outline it will measure at its thickest part, which is at its centre, four or less millimetres, while the organ is held in its position by the firm connective tissue that surrounds it. Over its surface, superficially, it is easy to discern the ramifications of the vein that comes away from it and thereafter joins the internal jugular. A tendinous expansion, which arises from the outer surface of the superficial muscles near the hinder end of the mandible, is seen to spread out over this organ iu large subjects. It is narrow and rather strong at its commencement, to become very thin and closely adherent to the skin as its fibres diverge anteriorly. There seems to be scarcely any muscular tissue in this tendon, but I am inclined to believe that by its contraction in the living reptile the venom of the gland can be forcibly jetted through the ducts and so along the grooves of the teeth at the time of its bite. In my specimen the four ducts serve the anterior moiety of the organ, its hinder half being without these glardular conduits. Now, although the upper teeth of Heloderma suspectum are grooved, I fail upon dissection of the parts to find any gland present wherewith they might be supplied with poison. Indeed the skin overlying the latero-labial region is quite adherent to the skull alon°- its margin, while just above it, between the eye and the external nostril, the bases of the dermal tubercles and the underlying bone often coossify. There seems to be no reasonable doubt at the present time but that the secretion of these glands in Heloderma is of a poisonous nature, and that the injury caused by its injection into the circulation of living animals varies. Still further research is required before we can possess anything like a complete knowledge of its action upon different animals and under varying conditions. It is hoped that experiments tending to make clear such points will be undertaken by the scientific investigator from time to time. VIII. T H E OLFACTORY CAVITIES A N D THE O R G A N OF JACOBSON. With the very finest of wire saws I made both a transverse a longitudinal section through the narial chamber of one side in a specimen of Heloderma suspectum. The operation brought the structures of the region plainly into view ; but, so far as I was enabled to discover, it revealed nothing that seemed to depart iu any 15* |