under, or pass within the two posteiior transverse processes of the 
preceding vertebra. They differ in direction according to the 
place which they occupy. Those in the highest vertebra pass 
obliquely downwards, and those in the lowest, obliquely up- 
wards ; as may be seen in the vertebra a and b in Fig. 6, Plate II. 
The posterior transverse processes also grow broader and less ob¬ 
lique as the vertebra descend. The whole connexion and propor¬ 
tion of the processes is such, that the greatest downward flexion 
takes place at the top of the curve, and the greatest upward flexion at 
the bottom ; an arrangement admirably adapted to increase the 
power of the muscles which act in the vertical flexion of the spine. 
The ribs are articulated by a double cavity to a small double 
headed process under the anterior transverse process of each ver¬ 
tebra. They differ in length and direction, those at the bottom 
of the curve being shorter and more spreading than those at the 
top, so that' the lower extremities of the whole fall in a right 
line. 
Muscles .—The principal muscles on the outside of the trunk con¬ 
sist of three strong dorsal muscles with oblique fibres continually 
arisingfrom the vertebral processes,or ribs,and inserted byan apon¬ 
eurosis into other bones of a similar kind. Below these is a broad 
thin lateral muscle or congeries of muscles, connected to the ribs 
only. These muscles according to their situation act in perform¬ 
ing the various inflexions of the body. 
On the jnside of the ribs a series of their muscles was ob¬ 
served, arising from the bodies of the vertebra, passing obliquely 
downwards and forward under three ribs and over the fourth, 
and afterwards inserted into ribs beyond. These muscles in con¬ 
junction with others, according to Sir Everard Home and other 
authors, act upon the ribs in serpents to assist their progressive 
motion on land. 
