70 
ON THE PHYSIOONOMY OF SERPENTS. 
ner different from its usual modes, and presents the colours of 
the Ophidians under a light much less agreeable than just 
after the casting of the skin. 
It results from the principles just laid down, that the 
form of the scales ought to depend on the direction of the 
movements executed by the organs they protect. The 
scales of the trunk are consequently disposed in lines paral- 
lel to the contour of the ribs : the lines are intersected 
by other lines at different angles, and thus the edges of the 
scales are formed. The greater or less regularity in the 
form of the scales depends on the respective direction of 
those lines : if those lines cross each other at right angles, 
the scales will be of a square form ; if, on the contrary, 
one of those lines be more inclined than the other to the 
axis of the trunk, the scales will be rhomboidal, and will 
approach to the lanceolate, or even the linear form, accord- 
ing as these lines are less or more divergent from each 
other. It happens almost always that these lines deviate 
from their original direction in curving themselves to join 
the middle range of plates below the animal ; hence the 
form of the scales becomes more irregular as they recede 
from the back, although they increase in size. It is uni- 
formly on the anterior part of the trunk that these lines, 
particularly those passing backwards, are inclined to the 
axis of the body ; hence the form of the scales, which 
cover that part of the body, should be assumed as the type 
in descriptions. Towards the tail, and on that member, 
the lines cross at almost a right angle, and these scales 
consequently become less irregular. The different form of 
the scales, on the different parts of the same individual, is 
very apparent on the Naja and the Xenodon, where the 
ribs of the neck, less arched than the others, and suscep- 
tible of a considerable movement from behind to the front, 
produce an enlargement of the volume of the body later- 
ally. In the state of repose, the scales of this part cover 
each other by their lateral edges ; they are in form nar- 
now or linear, while those of the tail, imbricated in the 
usual manner, are of a square form. 
The number of longitudinal ranges in which the scales 
are disposed, vary not only according to the species ; these 
