12 



elongation of this part of the spinal chord ; the space between the 

 lower filaments forming the root of one ner^'e, and the upper filaments 

 of the root of the succeeding nerve was not more than the space be- 

 tween the individual filaments of each root ; whence it would seem 

 that the elongation of the cervical portion of the chord was produced 

 by a general and uniform interstitial deposition during foetal develope- 

 ment, which thus effected an equable separation of these filaments ; 

 so that a single nerve, as in the case of the third cervical, might derive 

 its origin from a space extending six inches in length. 



The brachial plexus was principally formed by the first two dorsal 

 nerves ; seventeen pairs intervened between it and the large nerves 

 forming the lumbar plexus. 



The recurrent nerves were formed by the reunion of several small 

 filaments derived from the nervus vagus at different parts of its course 

 down the neck, instead of originating as usual in the thorax, and 

 being reflected, as a single nerve, round the trunks of the great 

 vessels. 



The sympathetic nerve in the neck was found to present five gan- 

 glionic enlargements of various sizes. 



Muscles. 



In the dissection of the abdominal muscles no peculiarity of im- 

 portance was noticed ; but in the neck there existed a highly inter- 

 esting modification of the parts which effect the retraction of the os 

 hyoides. The pair of muscles which, as in some other Ruminants, 

 combines the offices of sterno-thyroideus and sterno-hyoideus, arose 

 in the Giraffe by a single long and slender carneous portion from the 

 anterior extremity of the sternum ; this fleshy origin was nine inches 

 long, and it terminated in a single round tendon six inches in length ; 

 the tendon then divided into the two muscles, each division beco- 

 ming fleshy, and so continuing for about 16 or 18 inches ; then each 

 muscle again became tendinous for the extent of two inches, and 

 ultimately carneous again, prior to being inserted in the side of the 

 thyroid cartilage, and continued thence in the form of a/ascia into 

 the OS hyoides. 



Mr. Owen observes that this alternation of a non-contractile with a 

 contractile tissue, as exhibited by the above structure, displays in a 

 most striking manner the use of tendon in regulating the amount of 

 muscular contraction. Had the sterno-thyroideus been muscular 

 throughout its entire length, the contraction of its fibres would have 

 been equal to draw down the larynx and os hyoides to an extent quite 

 incompatible with the connections of the adjacent parts ; but the in- 

 tervention of long and slender tendons duly apportions the quantity 

 of contractile fibre to the extent of motion required. 



The muscle analogous to the omo-hyoideus of other animals was 

 adjusted to its office by a more simple contrivance, arising from 

 the third cervical vertebra instead of the scapula, the diminished 

 length of the muscle enabling it to act upon the os hyoides with the 

 requisite power of contraction. 



Mr. Owen remarks that the analogue of the sterno-mastoideus 



