SPINAL AND SYMPATHETIC NERYES. 709 



which is another very important step towards perfecting the auditory 

 apparatus. 



(2003.) Neither must we omit to mention that in the highest of the 

 Reptilia, as for example in the Crocodile, the first rudiment of a cochlea 

 makes its appearance, although as yet in a form of extreme simplicity. 

 This portion of the organ of hearing, which, from the elaborate struc- 

 ture that it presents in the higher Yertebrata, must be regarded as 

 being importantly connected with correct audition, is seen in this the 

 earliest stage of its development to be a simple conical appendage to the 

 sac of the vestibule ; and on opening it, it is found to be divided by a 

 central cartilaginous septum into two compartments, which are, how- 

 ever, continuous with each other at the apex of the cone. One of these 

 compartments or canals opens at one extremity into the vestibule, while 

 the other communicates with the tympanic cavity by a very small aper- 

 ture closed with a thin membrane. Thus, therefore, although the entire 

 organ resembles a simple canal bent upon itself, the representatives of 

 the scdla vestibuli, of the scala tympani, and of the fenestra rotunda of 

 the human ear can be distinctly identified. 



(2004.) The glosso-pharyngeal and pneumogastric nerves in Reptiles 

 supply the same organs to which they are distributed in the human 

 subject, the former being destined to the base of the tongue and the 

 muscles of the pharynx, while the latter, assuming a plexiform arrange- 

 ment, are appropriated to the lungs and heart, as well as to the oeso- 

 phagus and the stomach. 



(2005.) The hypoglossal pair of the cerebral nerves, which was not 

 met with in fishes, now becomes distinctly apparent, and, as in the 

 higher Yertebrata, may be traced in the muscles of the tongue. 



(2006.) The spinal system of nerves offers no peculiarity worthy of 

 special description. In the annexed figure, taken from Bojanus, the 

 nerves derived from the medulla spinalis are seen to issue in the usual 

 manner from the intervertebral foramina ; and they evidently essentially 

 correspond with the grand type of structure common to the vertebrate 

 classes. In the apodous Reptilia, as for example in the Serpents, to 

 attempt to divide them into the usual regions is clearly absurd ; but in 

 quadrupedal forms, as for instance in the Tortoise, the cervical nerves, 

 the brachial plexus, from which are derived the nerves of the anterior 

 extremity, the intercostal nerves, and those forming the lumbar and 

 sacral plexuses are at once distinguishable, and the correspondence 

 between their distribution in the reptile and in the human subject must 

 forcibly strike the student who makes the comparison. 



(2007.) Neither does the sympathetic system of the Reptilia offer any 

 important aberration from that arrangement with which the human 

 anatomist is familiar. The ganglia are smaller in their proportionate 

 size ; those, indeed, of the neck and face are scarcely perceptible ; but 

 the thoracic ganglia are found in their usual positions, communicating 



