OF THE MUSCLES. 35 



and having on their inferior extremity an articulating sur- 

 face more or less grooved, which produces a hinged junc- 

 ture with the condyle of the loAver jaw. The mastoids 

 are rarely firmly united to the skull, as in the Tortrix ; 

 more frequently appearing in the form of a scale, are always 

 placed in the same plane with the surface of the cranium, 

 and yield in size to the tympanites ; the form and direction of 

 which vary much in the different species ; the last-mentioned 

 bones are stout, and suspended nearly perpendicularly in 

 the Elaps, the Boa, the Tortrix, and several other non- 

 venomous serpents ; they are slender, filiform, directed 

 outward, and in a position more or less vertical in many 

 Ophidians, especially in the division of the venomous 

 snakes properly so called. 



It results from the conformation of these parts, that the 

 mouth of the Ophidians is more susceptible of enlargement, 

 according as the bones which suspend the lower jaw have 

 acquired a greater development, and as those composing 

 the upper jaw are more free. If, on the contrary, as in 

 many Ophidians, these last are bound together and to the 

 skull, if their tympanites are small, the bones acquire a 

 greater solidity or diameter, and the mouth is capable of 

 a less degree of dilatation. 



OF THE MUSCLES. = 



Several naturalists have applied themselves to describe 

 the muscles of Ophidians. Sir Everard Home * has fur- 

 nished some interesting observations on this subject. We 

 owe to M. HiJBNER,f a physician of Berlin, a dissertation 

 in which the author describes the organs of motion in the 

 Boa Canina ; but this academic tract is rarely met with 

 in libraries. MM. Duges | and Duvernoy § have pub- 

 lished descriptions and good figures of the muscles of the 

 head. The researches of Meckel || on the muscles of 



* Phil. Trs. 1810 ; and Lect. on Comparative Anatomy. 



* De organis motoriis Boce Canince, 

 X Annates de Sc. Nat. torn. xii. 



§ Ibid, t. xxvi., pi. 10. 



II Vergl. Anat. vol. iii. p. 130. 



