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 lower 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 Everarh Home ^ has fur- 
nished some interesting observations on this subject. Yfe 
owe to M. HuBNERjf 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. DugesJ and DuvER]sroY§ have pub- 
lished descriptions and good figures of the muscles of the 
head. The researches of Meckel || on the muscles of 
Phil, Tvs. 1810 ; and Lect. on Comparative Anatomy, 
I Pe organis motor Us Boi^e Canines, 
t AnnaUs de Sc. Nat. tom. xii. 
§ Ibid, t. xxvi., pi. 10. 
II Vergl, Anat. vol. iii. p. 130. 
