370 



REPORT OF NATIONAL MUSEUM, 1893. 



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 more fully. 



Prof. Wyman's account of some dissections of the poison apparatus 

 of the Eattlesnake was read at a meeting of the Boston Society of 



Fig. 19. 



LONtilTUDINAL SECTION 



FANCJ OP BOTHROPS 



Enlarged, a Poison duct entering 

 the fang at a'; a" opening of poison 

 canal near tip of fang ; 6 pulp cavity ; 

 c dentin; d connective tissue. 



(After Niemann.) 



Fig. 20 



TRANSVERSE SEC- 

 TION OF BOTH 

 HOPS FANG. 



* Beitrtige zur Morphologie und Physiologie der Oberlippendriisen einiger Ophidier. 

 Wiegmanii's Arcliiv f. Naturg., LViii, i, pt. 3, Sept., 1892, pp. 262-286 + pi. xiv. 



In spite of the apparent conclusiveness of Mr. Niemann's figures, I am compelled 

 to remark that his paper contains several indications of carelessness Avhich makes 

 it imperative to receive his conclusions with extreme care. That anyone should 

 attempt an investigation of that kind without knowiug and quoting Dr. S. Weir 

 Mitchell's epoch-making labors, is scarcely reassuring in the first place, but there 

 seems to be even less reason for a confusion of such terms as Solenoglyph for Opis- 

 toglyph on p. 282, and the mistaken identification of the ectopterygoid bone for the 

 maxillary, pp. 277 and 279. 



