ormnu. 



OPHIDIA. 



M ft exiett ! the Viper, and subsequently received addi- 

 _ tmhasllnn by Mr. Smith t panful examinations of the fangs of 

 UM tfvatrat, >'/, sad CntaJiu, and by Mr. Clift's illustrative draw- 

 ing* appended to Mr. Smith's paper. A true idea of the structure of 

 pain-bag will be formed by supposing the crown of a simple tooth, 

 M that of m /lee, to be {iinsiJ flat, aad its edges to be then bent 

 toward* rach other, aad soldered together to aa to form a hollow 

 cylinder open at both ends. The flattening of the fang, and it* 

 bittllnn around the poison duct, commence Immediately above the 

 base, sod the suture of the inflected margins runt along the anterior 

 aad convex side of the recurved fang ; the poison-canal is thus in 

 front of the pulp-cavity. The basal aperture of the poison-canal is 

 oblique, aad iu opposite outlet U still more so, presenting the form of 

 a narrow elliptical Witudinal fissure, terminating at a abort distance 

 from the apex of the bog. 



" The ubuacttr meet commonly adduced from the dental system, 

 at dsOiagulshing UM venomous from the non-venomous serpent*, is, 

 that the former have two, the latter four, rows of t.-eth in the upper 

 jaw ; the two outer or maxillary row* being wanting in the venomous 

 HilfllM. tad their place being supplied by the single pouon fang. The 

 exceptions to tb.ii rule are however too numerous for it* value as a 

 <lMllnt.iii*liliH character in a question of such practical moment as 

 UM venomous or non-venomous properties of a serpent. In all the 



family of Marine Serpents the 

 row of fixed maxillary teeth. 



is only the foremost of a 

 the liydrvpku it rial** there are 



four treth, and in Hgdnpkit seaufoto five teeth, behind the venom- 

 rather unaller MM than it; the Two-Coloured Sea-Snake 



Mester) has also five maxilUry teeth in addition to the 

 perforated one. The poison-fang in this genus U relatively smaller 

 than in the venomous serpent* of the land, but present* the same 

 peculiar structure. The poison-gland presents a correspondingly small 

 devdopmeot ; it is pyriform, ana it* structure, according to Dr. Cantor 

 ( Zool. Trans.,' vol. it p. 304), is minutely cellular ; it is covered by 

 the apooenrotic expansion of the articnlo-maxillaris, and transmits a 

 straight duct horizontally to the basal opening of the venom-fang. 

 It it a curious fact that the smaller non-venomous teeth of .the poisonous 

 serpents all present a trace of the structure of the functional venom- 

 fang, being more or lea* deeply grooved along the convex anterior side ; 

 tad in the llydna tbU groove commences by a depression analogous 

 to the oblique basal aperture of the poison-canal in the true fang. 



" The colubriform poisonous serpents of the land have compara- 

 tively abort venom-fangs, but they are larger than those of the pelagic 

 serpent* ; and behind the venom-fangs there are likewise some smaller 

 grooved teeth in the maxillary bones ; there are three such teeth in 

 the B*yant Pama, sad five in the Sttnganu annulalia. 



or Oreat Hooded Poisonous Tree-Snake of 



In the 

 India, the 



venom-butt; is relatively as large as in typical poisonous serpents, but 

 three or four smaller grooved teeth are implanted behind it on the 

 maxillary bone. 



" In the most deadly venom-snakes, M the Viper (Strut), the Puff- 

 A.I Irr ( Viftn), the Asps or Hooded Snakes (Xaja), the Rattle-Snakes 

 (CVWo/u), and the Cophia* tad Fer de-Lance (Trigonocrphalta), the 

 poison-fug* acquire their largest sixe, and are associated only with 

 their iiicosstui*. These are clustered in greater or lees number behind 

 them, iittttiilliig the tame structure, but of a size proportionate to 

 their degree of development, and further differing m being loosely 

 Imbedded in the thick and wide mucous gum, which likewise conceals 

 UM fixed tad functional bng in its ordinary position of retraction and 

 repose. This (tag b more strongly curved backwards than the ordi- 

 nary teeth, but its acute and slender apex is frequently bent slightly 

 in the contrary direction, M in the Rattle-Snake. 



"The menhsnitm by which the abort maxilUry bone and the 



a bag are rotated backwards aad forwards upon the ginglymoid 

 be* connect* the maxilUry with the pnrfrontal and palatine 

 MI already been noticed ; sad aa some description of the secret- 

 big apparatus to which the peculiar modification of the venom-fang 

 it subservient might here be expected, I have selected for it* illus- 

 tration the accurate figure which Professor Miiller hat given of the 

 salivary tad poboo-gUndt in the Trigonoetplulut Umctolatut, in l.U 



em. (' De OUndularum Scernentium 

 fig. 1. p. 65.) 



M The poison-gUod* occupy the sides of the potrior half of the 

 d; eaeh lonilili of a number of elongated narrow lobes, extending 

 fro* UM main duct which runs along the lower border of the gland 

 upwards aad slightly backwards. Kach lobe gives off lobules through- 

 out rt* extent, thus presenting a piunatifid structure ; and each 

 lobule it subdivided into smaller .eotmilng circa, which constitute the 

 Ithnili structure of the gland. The whole gland is surrounded by a 







. of which the outermost and strongest 

 with the muscles by wbone contraction the 

 and lobre of the gland are compressed and emptied of 

 thfir Mention. Tbi* is then conveyed by the duct to the basal 

 anrtur. of the poisoo-canal of the (sag. We may suppose, that a* 

 the analogous lachrymal and aalivary gUnd* in other animal* are most 



active during particular emotion*, so UM rage which stitnuUtes the 

 ~ use its deadly weapon must be accompanied with an 

 Ion and great dimension of UM poison-glands ; and as 



U action of UM 



muscles it 



With :. 



blow by which the serpent inflicts its wound, the poison is at the same 

 moment injected with force into the wound from the apical outlet of 

 the perforated fang. 



" The duct which conveys the poison, although it runs through the 

 centre of a great part of the tooth, is nevertheless, a* we have seen, 

 really on the outside of the tooth, the canal in which it is lodged and 

 protected being formed by a longitudinal inflection of the pariotes of 

 the pulp-cavity or true internal canal of the tooth. This inflection 

 commences a little beyond the base of the tooth, where its nature is 

 readily appreciated, as the poison-duct there rest* in a slight groove 

 or longitudinal indentation on the convex side of the fang ; as it pro- 

 ceeds it sinks deeper into the substance of the tooth, and the sides of 

 the groove meet and seem to coalesce, ao that the trace of the inflected 

 fold ceases in some species to be perceptible to the naked eye ; and 

 the fang appears, as it is commonly described, to be perforated by the 

 duct of the poison-fang. 



" From the real nature of the poison-canal, it follows that the 

 transverse section of the tooth varies in form in different parts uf the 

 tooth ; at the base it is oblong, with a large pulp-cavity of a corres- 

 ponding form, with an entering notch at the anterior surface ; farther 

 on, the transverse section present* the form of a horse-shoe, and the 

 pulp-cavity that of a crescent, the horns of which extend into the 

 sides of the deep cavity of the poison-fang. A little beyond this [art 

 the section of the tooth itself is cresceatic, with the horns obtuse and 

 in contact, so as to circumscribe the poison-canal ; and along the 

 whole of the middle four-sixths of the tooth the section show.- the 

 dentine of the fang inclosing the poison-cavity, and having its own 

 centre or pulp-canal, in the form of a crescentic fissure situated close 

 to the concave border of the inflected surface of the tooth. The 

 pulp-cavity disappears, and the poison-canal again assumes the form of 

 a groove near the apex of the fang, and terminates on the anterior 

 surface in an elongated fissure. 



" If the end of each inflected fold of cement in the tooth of the 

 Labyrinlliodon were dilated sufficiently to contain a tube, that tooth 

 might convey the ducts of fifty poison-glands deeply imbedded in iU 

 substance, and yet all of them actually on the outside of the tooth 

 itself; it is the existence of a single fold of the same kind, but more 

 simple, inasmuch as it is straight instead of wavy, which forms the 

 complication of the viper's fang subservient to the completion of its 

 peculiar offensive weapon. 



" The venom-fangs of the Viper, Rattle-Snake, and Fer-de-Lance arc 

 coated only with a thin layer of a subtransparent and minutely 

 cellular cement The disposition of the calcigerous tubes is obedient 

 to the general law of vertically to the external surface of the tooth. 

 Since the inflected surface of the tooth can be exposed to no other 

 pressure than that of the turgescent duct with which it is in contact, 

 the tubes which proceed to that surface, while maintaining their usual 

 relation of the right angle to it, are extremely short, and the layer of 

 dentine separating the poison-tube from the pulp-cavity is propor- 

 tionally thin. The calcigerous tubes that radiate from the opposite 

 side of the pulp-cavity to the exposed surface of the tooth are dispro- 

 portionately long. 



" The pulp-cavity, following the form of the tooth itself, presents 

 in a transverse section of this part the form of a fissure describing 

 four fifths of a circle ; the fissure is widest at the middle and at the 

 two extremities ; the exterior calcigerous tubes, in quitting the pulp- 

 cavity, form a graceful curve, the convexity being turned towards the 

 nearest born of the crescent ; at the middle of the pulp-fissure the 

 tubes proceed straight to the opposite surface ; and at the two extremi- 

 ties of the crescent the central tubes are nearly straight, while the 

 lateral ones radiate in graceful curves which become bolder as they 

 diverge from the central and straighter tubes. Throughout the greater 

 part of the tooth the calcigerous tubes describe their various inflec- 

 tions in a plane transverse to the axis of the tooth ; but towards tho 

 apex they begin gradually to rise from that plane; and as the pulp- 

 cavity reassumes, with the tooth itself, the simple conical form beyond 

 the termination of the poison-canal, the calcigerous tubes extend to 

 equal distances from the linear remnant of the pulp-cavity, which has 

 again passed to the centre of the tooth, and those tubes which are 

 continued from its extremity pass to the apex of the fang in a line 

 parallel with the axis of the tooth. The calcigerous tubes present 

 secondary curvatures of a slightly wavy character, which become more 

 marked and irregular near their termination. In whatever part of 

 the section an entire tube could be clearly traced to its termination, 

 it formed an anastomotic loop at the periphery of the dentine with 

 an adjoining tube. The calcigerous tubes present a diameter of the 

 l-18,000th of an inch, nnd they are separated by interspaces equal to 

 four of their own diameters. Each calcigerous tube gives off IMMMV 

 primary branches in its course, but is rarely seen to divide dichoto- 

 mou*ly until it begin* to form its irregular sinuosities near the peri- 

 phery of the tooth. In the transverse section, the primary branches 

 an sent off from the concave side of the tube, at an acute angle 

 with the trunk ; the secondary smaller and more numerous branches 

 proceed from the same side of the main tube or of its primary 

 branches, at a loss acute angle, into the clear uniting substance ; they 

 are remarkably parallel with each other and straight. In old poison- 

 fangs the pulp-cavity or fissure is obliterated by ossification of the 

 remains of the pulp. 



