12 



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

 lower filameiits forming the root of one nerve, 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 ; vvhence it vrould seem 

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

 by a general and uniform interstitial deposition during fcetal develope- 

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

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

 its origin from a space extending six inches in length. 



The brachial plexus was principallj' 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 differentparts of its course 

 dovi'n 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 museles no peculiarity of im- 

 portance \vas 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 museles ■vvhich, as in some other Ruminants, 

 combines the offices of sterno-thyroideus and sterno-hyoidev.s, arose 

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

 anterior extremity of the sternum ; this fleshy origin \vas nine inches 

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

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

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

 musele 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 afascia into 

 the os hyoides. 



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

 contractile tissue, as exlubited b)^ the above structure, displays in a 

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

 muscular contraction. Had the sterno-thyroideus been muscular 

 throughout its entire length, the conti'action 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 tendon s dūly apportions the quantity 

 of contractile fibre to the extent of motion reąuired. 



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

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

 the third cersical vertebra instead of the scapula, the diminished 

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

 reąuisite po\ver of contraction. 



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



