372 REPORT OF NATIONAL MUSEUM, 1893. 



exodus iias been forced, the gum escapes with Liceration only. lu either case, how- 

 ever, the gum remains as a barrier, limiting the progress of the advancing reserve 

 fang; and while the latter is establisliing itself provisionally the gum encircles it, 

 clasps it tenaciously, and l>rings 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 first fang of reserve is againdis- 

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



as stated by ])r. Johnston, the tirst reserve fang enters the semilunar 



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



to find the two fixed fangs unsymmetrically 



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



Q side, of their respective sockets, or both on the 



7 /^'"'"T^^^L-.C^^^ inner side; or again, both on the outer side. 



^V.~)^ "^ He also expressly states that in all other points 



^"" \Q / 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. 



^''^'■"'" ^.,^ I have previously mentioned the special 



DIAGRAM II,LUSTRATII>'G THE Sl'C- 1 J 1 



CESSION OK THE FANGS. musclcs ciigaged in erecting and depressing the 



a Alveolar socket; 6 functiou- ^ j ^^^^^ now Call attention to thosc 



ary fang; cits successor; d tbe • i i i i • 



next fang in order of age; ere- whlch forCC the pOlSOU thrOUgh the dUCt mtO 

 niaining germs. fhc liollow faug. 



(After Mitchell. ) , i i • r> ^i 



In the uon-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 

 l)one; 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 quadrate 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 upper 

 one, or, in other words, to close the moutli. The anterior temporal (^), 

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

 stead of connecting with the cranial Avail, it has lost all connection with 

 the latter and arises Irom the upper posterior portion of the firm, tendi- 

 nous capsule of the poison gland («), runs backward under the ribbon- 

 like ligament [e] which fastens the gland to the joint of the jaw, winds 



