224 



TROPICAL MEDICINE AND HYGIENE 



subjacent to the rostral ; and two pairs of chin-shields 

 (c.s.), one behind the other, immediately posterior to 

 the first lower labial. Between the chin-shields in most 

 snakes is a longitudinal furrow, the mental groove (m.g.), 

 which permits lateral stretching of the mouth. 



As regards the snake's skull, we need only consider 

 those bones that enter into the formation of the jaws 

 and palate, as displayed in a harmless Colubrine snake 

 {figs. 95 and 96) : a very rough dissection is all that is 

 necessary to expose them. 



p.m 



Somewhat Diaarommatic 



FIG. 95. 



In all snakes the lower jaw, and in many snakes the 

 backstay of the bony palate and upper jaw also, are slung 

 at the end of a long mobile quadrate bone (q.), which 

 hangs freely from the cranium on either side. In most 

 snakes the quadrate does not articulate directly with the 

 cranium, but, for increased mobility, is attached to a 

 longish bone, the squamosal (sq.\ which lies loosely on 

 the cranium. Each ramus of the mandible, or lower jaw, 

 is composed of several bones, among which an articular 

 (ar.) and a dentary (d.) are always recognizable : the 

 articular, which is toothless, articulates with the quadrate, 

 and is firmly spliced into the dentary, which usually bears 



