. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. 370 REPORT OF NATIONAL MUSEUM, POISON The external covering of the gland is made up of two more or less distinct layers of fibrous tissue, the outer one being continued pos- teriorly in a ribbon-like ligament running backward and inserting itself upon the joint of the jaw (fig. 18, e). A short ligament on the side _ ^ _ _ facing the skull attaches the gland firmly to the latter, and a third one below con- nects with the external pter
. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. 370 REPORT OF NATIONAL MUSEUM, POISON The external covering of the gland is made up of two more or less distinct layers of fibrous tissue, the outer one being continued pos- teriorly in a ribbon-like ligament running backward and inserting itself upon the joint of the jaw (fig. 18, e). A short ligament on the side _ ^ _ _ facing the skull attaches the gland firmly to the latter, and a third one below con- nects with the external pterygoid nuiscle (fig. 15, c). At the anterior end of tlie gland the cap- sule continues as the outer covering of the duct which carries the poison from the gland to the fang. This duct, in its normal posi- tion, makes a sudden upward curve (fig. 18, fl') under the eye, descending from which it follows the i^osterior wall of the pit and finally passes over the rounded outer front edg(^ of the maxillary bone, at the base of which it meets the upper opening, or inlet, of the canal through the fang. Until Prof. Jeffries Wyman, in 18G0, and, about simultaneously, Dr. Christopher Johnston, i^ublished opinions to the effect that the poison duct does not enter the canal of the fang, it was generally held that it actually continued inside of the channel. This latter view has been revived quite recently by Dr. F. Niemann, who not only describes this arrange- ment, but figures longitudinal and transverse sections of it as seen by him in a crotaloid snake, Bothrops lanceolatus* The longitudinal section is reproduced here as fig. J9, the transverse one as fig. 20, The latter shows at a^ the poison canal lined with the duct, which, even inside of the fang is characterized by its epithelial lining. As this opens up the question again, and makes future research necessary, and as Mr. Niemann seems to be ignorant t of the investigations referred to, it may be well to quote their evidence a little
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