26 ON THE PHYSIOGNOMY OF SERPENTS. 



testine, that the same organs ^Yhich in other vertebrata 

 occupy one or more spacious cavities, are packed in Ophi- 

 dians, on account of the elongated shape of their trunks, 

 in a long, narrow cylinder. It is ob\ious that this dispo- 

 sition could not have taken place ^^^thout gi*eat clianges in 

 the formation of the viscera, and without disturbing bila- 

 teral symmetry. On this account, the heart is sometimes 

 far removed from, at other times approximated to, the 

 head, according to the greater or less capacity of the sto- 

 mach ; for the same reason, we often find but a single lung, 

 sometimes before the heart, but generally placed beliind 

 that organ. This lung almost always terminates in a sort 

 of sac, of greater or less size, serxdng as a reservoir for air. 

 The form of the liver, for the same reason, is modified into 

 a narrow riband, extending from the heart to the pylorus. 

 The gall-bladder, that it might not be impeded in its func- 

 tions when the stomach is full, is removed from the liver, 

 and is placed in the same curvature of the duodenum which 

 receives the pancreas and the spleen. The stomach re- 

 sembles a long, not very wide, cylinder. The intestines 

 succeed, the numerous inflections of which are filled vdth 

 fat, and, after descending in a straight line, terminate in the 

 cloaca. The inferior part of the abdomen, not being suf- 

 ficiently capacious to receive the other organs, is the cause 

 of the anomalous position of the kidneys, the testicles, and 

 the ovaries ; hence, the penis and the secreting organs are 

 lodged m the tail. 



It is evident from what we have said, that the form of 

 the greatest part of the internal organs of serpents has 

 no influence on the exercise of their functions ; we shall 

 afterwards even see that the position of these organs not 

 only differs in different species, but sometimes varies among 

 indi\'iduals of the same species. 



The disposition of the external organs, on the contrary, 

 presents more constant forms ; but these parts are modified 

 according as the species inhabit trees, the gi^ound, or the 

 water. Locomotion, however, is exercised very uniformly : 

 the same movements make the snake glide on the ground 

 which impel it through the depths of the humid element, 

 or which serve to entwine it around the branches of trees. 



