SUPPLEMENT. 415 



to their situation, act in performing the various inflexions of 

 the body. 



On the inside of the ribs a series of their muscles was ob- 

 served, arising from the bodies of the vertebras, passing ob- 

 liquely downwards and forward under three ribs and over the 

 fourth, and afterwards inserted into ribs beyond. These mus- 

 cles, in conjunction with others, according to Sir Everard Home 

 and other authors, act upon the ribs in serpents to assist their 

 progressive motion on land. 



Viscera. The only part of the viscera, which the limited 

 openings permitted us to examine, were a portion of the lung 

 and oesophagus with the mesentery and blood vessels, also a 

 small part of the stomach. The lung was a long cellular and 

 tubular viscus, as in other serpents, but with this remarkable 

 peculiarity. It was successively dilated and contracted so as 

 to adapt itself to the cavities formed by the undulations of the 

 spine. The oesophagus was also unequal, but without relation 

 to the cavities of the spine, not being in contact with it. In 

 the stomach was found a mass of scales, also the tail and part 

 of the skin of a serpent of a different species, having all the 

 scales carinate. 



In regard to the use or final cause of the curvatures in the 

 back-bone, which give so peculiar a character to' this animal ; 

 it is obvious that two important ends are effected by it. These 

 are an increase of flexibility and an increase oLstrengtlt in 

 vertical motions. 



1. The flexibility is increased, because in any given length 

 of body, there will be more joints in a crooked, than there 

 would be in a straight spine, composed of vertebras of the same 

 dimensions. 



2. The strength in vertical motions is increased, since the 

 fulcrum formed by the highest articulation is more remote 

 from the power applied by the lateral muscles, and the fulcrum 

 formed by the lowest articulation, is also more remote from 



