322 NATURAL HISTORY. 



The pre-maxillary bones are very small and toothless. The maxillary bone has not the 

 elongate shape of that of the non-poisonous Snake, but it is short, somewhat bag-like, and hollow, 

 and a long curved fang is on that part of it which resembles the bottom of the bag, and which, in 

 the position of rest, looks backwards along the palate. Hence, when quiet, the fang is hidden in 

 folds of the soft tissues of the roof of the mouth. The hollow of the bone is below the pit in front of 

 the eye. The upper and inner part of the maxilla is jointed with a pulley -like surface on the lachry- 

 mal bone, so that the bag-like maxilla and its tooth can move forwards and backwards on the 

 lachrymal bone, the end of the fang describing about a quarter of a circle, and being vertical when 

 at the fullest forward movement in the striking position. The lachrymal bone has some movement 

 on the frontal bone. Now, the mechanism of the bones of the palate and of the side of the head has 

 to produce a forward and backward movement of the free end of the maxillary bone ; and it has 

 especial connection with the necessity of the fang being vertical and ready to strike when the mouth is 

 widely open, and of the curving back of the fang along the palate, out of harm's way, when the mouth 

 is shut. 



The fang, and its supporting bone hinged on to the lachrymal bone, can be pushed forward as 

 the mouth opens in the following manner : There are three bones on each side of the mouth whose 



names are already very familiar, and they are, a small 

 palate bone armed with curved teeth ; a long, flat, bar-like, 

 transverse bone, and the pterygoid bone, which is long 

 and stout, and as usual is united behind with the quadrate 

 bone close to the lower jaw. The transverse bone is 

 attached in front by a hinge-like joint with the maxilla, 

 and behind it is connected with the pterygoid. The palate 

 bone is also attached to the pterygoid by a joint, and is 

 connected by fibrous tissues with the skull. These bones 

 form a long line, and as a whole they are in contact with 

 the quadrate bone behind, and with the upper edge of the 

 hinder part of the tooth-bearing maxilla in front. The 

 quadrate bone and the maxilla being movable on the skull, 



HBAD OF RATTLESNAKE, SHOWING FAXGS, AND 



MUSCLES OF POISON GLANDS. the motion of the first is conveyed to the latter fang- 



bearing bone by means of the intermediate rod. Now, 



"\vhen the mouth is shut, the quadrate bone is placed so that it reaches out from the squamosal 

 bone, on the side of the skull, downwards and backwards, and the pterygoid bone with its 

 prolongation, the transverse, is pulled backwards. So that the hinder part of the maxilla is pulled 

 backwards, and the fang i*ests on the mucous membrane of the palate. When the Snake opens 

 its inouth to strike, the lower jaw separates from the upper, and the quadrate bone is pushed 

 forward at its end at the lower jaw. This movement acts on the line of bones ; he pterygoid is 

 pushed forwards, and the transverse also, so that a force acts on the maxilla tending to press it forward, 

 and to make its lower or toothed part move in a corresponding direction on the joint with the 

 lachrymal bone. This peculiar movement is the result of the combined movements of the transverse 

 and palatine bones and their joint or union with the pterygoid. 



The next proceeding is the snap or attempted closure of the jaws on the prey, and the same 

 muscle (or rather part of it) which closes the lower jaw on the upper compresses the poison 

 gland, which lies between it and the side of the skull above and behind the maxilla, and forces 

 a drop of its secretion down its duct which leads into the canal of the tooth. As soon as this is 

 done the mouth is closed, and the long bones pull on the maxilla and restore the fang to its place on 

 the palate. 



In the Zoological Gardens in the Regent's Park, London, the Rattlesnakes may be seen exercising, 

 as it were, their jaws, before the Guinea-pig, a favourite prey, is given them. They open the mouth 

 widely, and immediately the long, slightly-curved, slender fangs project well in front, and are at right 

 angles with the upper jaw. It appears as if each slipped out of an envelope of soft skin which never 

 quite leaves their base, or where they are attached to the maxillary bones. Then the mouth is shut 

 and the teeth are retracted during that operation. 



