MUSCULAR SYSTEM OF MAMMALIA. 47 



expanding behind the metatarsal, and splitting to perforate the 

 tendon of the preceding flexor in its way to the last phalanx. 



Of the abdominal muscles, the * obliquus externus ' is shown in 

 fig. 18, 14 ; its broad tendon is perforated by the mammary artery 

 and vein, at 19. The ( obliquus internus ' is seen at ig, fig. 19. 



I found the following conditions of the hyoid muscles in the 

 Giraffe : l — The ' mylo-hyoideus,' thick and strong, arose from the 

 internal surface of the lower jaw, and was inserted into the 

 raphe dividing it from its fellow of the opposite side. It ad- 

 hered firmly to the e genio-hyoideus :■ this arose by a well marked 

 tendon from the symphysis menti, and had the usual insertion. 

 The ' genio-glossus ' arose by a tendon close to the inner side 

 of the tendon of the ( genio-hyoideus ; ' its fleshy belly had a 

 considerable antero-posterior extent, and diminished to a very 

 thin edge at its anterior margin. The ' digastricus ' had the 

 usual origin, and was inserted, broad and thick, into the under 

 side of the lower jaw. The e stylo-hyoid ' was remarkable for the 

 slenderness and length of its carneous part. The most interesting 

 modifications in the muscles of the os hyoides were found in 

 those which retract that bone. The muscle which, as in some 

 other ruminants, combines the offices of the ' sterno-thyroideus ' 

 and ' sterno-hyoideus,' arose by a single long and slender carneous 

 portion from the anterior extremity of the sternum ; this origin 

 was nine inches long, and terminated in a round tendon, six inches 

 long ; the tendon then divided into two, and each division soon 

 became fleshy, and so continued for about sixteen inches ; then 

 each division again became tendinous for the extent of two inches, 

 and ultimately carneous again, when it was inserted into the side 

 of the thyroid cartilage, and thence continued in the form of a 

 fascia to the hyoid. This alternation of contractile with non- 

 contractile tissue gave a striking example of the use of tendon in 

 limiting the length of the contractile part of a muscle to the 

 extent of motion required to be produced in the part to which the 

 muscle is attached. Had the sterno-thyroideus been continued 

 fleshy as usual from its origin through the whole length of the 

 neck to its insertion, a great proportion of the muscular fibres 

 would have been useless ; for as these have the power of shorten- 

 ing themselves by their contractility one-third of their own 

 length, if they had been continued from end to end in the sterno- 

 thyroidei, they would have been able to draw the larynx and 

 hyoid one-third of the way down the neck ; such displacement, 

 however, is neither required nor indeed compatible with the 



1 xcvir. p. 232. 



