162 OUTLINES OF EQUINE ANATOMY. 



a sixth or cibducens nerve arises ; and more outwards and 

 posteriorly placed the glosso-2)haryngeal, pneumogastric, 

 spinal accessory, and lingual nerves, while the seventh and 

 eighth together arise immediately behind the fifth from the 

 lateral i^art of the medulla. The eleventh or spinal 

 accessory nerve arises from the lateral part of the spinal 

 cord as low down as the fifth cervical vertebrae. It runs 

 towards the cranium, passing between the sensory and 

 motor roots of the s^^inal nerves, receiving fibres from the 

 •lateral part of the cord. Its last fibres arise from the 

 medulla oblongata, it then emerges from the cranium 

 through the posterior part of foramen lacerum basis cranii, 

 and runs to supply sterno-maxillaris, levator humeri and 

 other muscles of the neck. It has extensive communica- 

 tion with the nerves near its origin and with the superior 

 cervical ganglion. The lingual nerve passes between it and 

 the glosso-pharyngeal. 



In laying open the cranium to examine its contents 

 remove all surrounding soft structures. Saw through 

 the forehead transversely about three quarters of an 

 inch above the orbital process of the frontal bone. 

 From the extremity of this incision divide the bones 

 on either side so as to remove the superior third of the 

 foramen magnum of the occiput. Eaise the separated 

 portion, calvarinm, with the chisel, the dura mater with its 

 falx cerebri will be seen attached to its internal surface. 

 The anterior part of the spinal cord having been now cut 

 through, the brain may be raised, and the nerves passing 

 from its base divided in turn from behind forward. The 

 olfactory bulbs will gener^ally remain in situ. The contents 

 of the cranium is termed the encephalon. 



The internal and middle ear may be examined by im- 

 mersing the petrous temporal bone in a solution of hydro- 

 chloric acid, three drachms of the acid to a c[uart of water. 

 (We have never tested this process practically, but have seen 

 it recommended.) After a time the bone will become dej^rived 

 of earthy matter so that it can be divided by a common scal- 

 pel. The foramina should be first stopped with w^ax, that the 

 ©ssicula auditus may remain uninjured. The petrous temporal 

 lone is the hardest bone in the body ; it is, therefore, well 

 calculated for communication of the vibrations of the 

 atmosphere. In it is situated the organ of hearing, which, 

 like all other organs of special sense, has certain nerve-cells 



