372 REPORT OF NATIONAL MUSEUM, 1893. 



exodus lias been forced, the giiin escapes with Liceration only. In either case, how- 

 e%er, the gnni remains as a barrier, limiting the i)r()gress of the advantnng reserve 

 I'ang; and while the latter is establishing itself provisionally the gum encircles lb, 

 clasps it tenaciously, and brings the poison papilla in opposition with its dental 

 aperture. As time passes, the new fang moves gradually outward to its permanent 

 seat; the inner maxillary recess is restored, and the iirstfang of reserve is again dis- 

 covered on the inner side of its senior, resting with its pulp attachment in the bot- 

 tom of the recess. Thus, the reserve fang has become an adult functioning fang, 

 nor does its pulp relax its hold until fate or mischance dislodge the now fatally- 

 armed tooth which it animates. 



Dr. Mitchell adds that although it is often, or usually, the case that, 

 as stated by T>r. Johnston, the first reserve fang enters the semilunar 

 socket in the maxilla to the inside of the active fang, it is not uncommon 



to find the two fixed fangs un symmetrically 

 placed, one on the inner, the other on the outer 

 f^ side, of their respective sockets, or both on the 

 inner side; or again, both on the outer side. 

 He also expressly states that in all other points 

 his own researches agree with those of Dr. 

 Johnston, and he presents the diagram, here 

 reproduced (fig. 21), to illustrate their views as 

 to the direction taken by the new fang in its 

 '' progress toward the alveolar socket. 



^^^'"^^'..r,^ „ ., I have previously mentioned the special 



DIAGRAM U.LUSTRATIIJG THE SUC- I J 1 



CESSION OF THE FANGS. musclcs eugagcd in erecting and depressing the 



a Alveolar socket; 6 functiou- f^j j ^^,^^y j^^^ ^^^ attention tO thoSe 



ary fang; cits succes.sor; d the 



next fang in order of age; ere- which forCC the poisOU thrOUgh the duct lUtO 



maining germs. ^Jjg holloW fang. 



In the non-poisonous snakes the closing of the 

 mouth is effected by the three temporal muscles, the anterior, the 

 middle, and the posterior. The anterior temporal arises from the 

 parietal crest and its continuation on the postfrontal bone, turns back- 

 ward around the joint of the lower jaw and is inserted on the latter 

 bone; the middle temporal arises from the posterior half of the parietal 

 crest, runs downward and forward under the former and is similarly 

 inserted, while the posterior temporal, the strongest of them all, arises 

 from the (inadrate bone and is inserted on the inside of the entire length 

 of the angular bone of the lower jaw. 



In the crotalids this arrangement is considerably modified (fig. 

 18). The posterior (c) and middle {g) temporal muscles remain essen- 

 tially as in the non- venomous snakes, and their function is also the 

 same, viz, by contraction to pull the lower jaw up against the ui^jjer 

 one, or, in other words, to close the month. The anterior temporal (/>), 

 however, has now both a difterent rise and a different function. In- 

 stead of (jonnecting with the cranial wall, it has lost all connection with 

 the latter and arises from the upper posterior portion of the firm, teudi 

 nous capsule of the poison gland {a), runs backward under the ribbon 

 like ligament (e) which fastens the gland to the joint of the jaw, winds 



