OF THE VENOM OF THE RATTLESNAKE. 9 



insertion along the inside of the palatal bone. As its fibres cross those of the 

 spheno-pterjgoid, its action antagonizes that muscle and aids the purpose of the 



Fi.n-. 3 



Myology. — Palatal view of the mtisoles of the upper jaw and base of the skull, a, spheno-pteiygoid muscle — the 

 elevation of the fang is caused by its action on the pterygoid and palate bones ; 6, external pterygoid muscle — the 

 retractor of the fang — inserted into the outside of the superior maxillary bone ; c, fascial sheath of this muscle 

 attached to the capsule of the venom gland ; d, spheno-palatine muscle. 



pterygoideus externus. The connection of the palate bone and the pterygoid bones, 

 which we have already noticed, is essential to this result. 



Almost all of the muscles about the head, neck, and jaws of the serpent, take 

 part either in the motions which precede the blow, or those which inflict and follow it. 

 Most of these muscles have functions which are obvious and easily demonstrable ; 

 and we shall, therefore, content ourselves with the briefest reference to all but the 

 anterior temporal, which plays a far more important part, and requires a fuller 

 description. 



The mouth is opened by muscles, such as the costo-mandibular and the vertebro- 

 mandibular, with the help of a muscular layer analogous to the platysma myoides. 

 The articulation of the jaws is fixed by the double action of the digastricus and 

 cervical angular muscles. 



Of the temporal muscles there are three. The anterior temporal. Fig. 4, a, 

 functionally the most important, arises from behind the orbit and from the upper 



Fiff. 4. 



Exhibiting the Relation op the Tempokal Muscles to the Venom Gland, a — a, auterior temporal muscle ; b, its 

 insertion in the lower jaw ; c, venom gland ; d, the fang half erected. 



