338 MR. A. H. GARROD ON THE [^P r - 4, 



In Plotus this uniformity is considerably disturbed, irrespective 

 of the above-described kink, by the excessive development of the 

 longus colli in its lower almost interthoracic portion, as well as, 

 though to a less degree, by the enlargement of the longus colli 

 •posterior behind. 



In Plotus anhinga, as above stated, there are 20 cervical vertebrae. 

 A small slip of the longus colli arises from the body of the third 

 dorsal vertebra, which is inserted into the transverse process of the 

 1 7th cervical. Above, and in contact with this, is another similar 

 slip to the 16th cervical. From the bodies of the 2nd and 1st 

 dorsal vertebrae, as well as from the antero-median portions of the 

 six lower cervical vertebrae, a large muscle arises on each side, in 

 layers (somewhat resembling the layers formed by the basally 

 expanded petioles of an onion bulb) — the lower being partially en- 

 closed in the upper — which ultimately form a bipenniform mass 

 with a tendon running axially through it and continually receiving 

 additions in the form of outer coverings of tendinous tissue arising 

 from the enclosing muscles, till it forms a strong single tendon which 

 courses up the front of the neck, close to the middle line on each 

 side, to be inserted into the downward-directed, peculiarly long 

 haemapophysial spine of the 8th cervical vertebra, and gives off slips, 

 on its way up, to the serially homologous processes of the 9th and 

 10th vertebrae. A similar tendinous slip to the 11th vertebra has 

 an independent origin from the bodies of the 15th and 16th verte- 

 brae, internal to the main muscular mass, which is almost the size of 

 a lemon, and with its fellow of the opposite side, of much the same 

 shape, filling up and projecting beyond the slight anterior con- 

 cavity above mentioned, formed by the mutual articulations of the 

 15th, 16th, 17th, 18th, and 19th cervical vertebrae. (In Plate XXVI. 

 figs. 1 & 2, these different details are clearly shown.) 



Posterior cervical region. — Here there is an exaggerated develop- 

 ment of muscle in the juxta-thoracic part, opposite the similar 

 enlargement in front, although it is not so considerable behind. 

 The longus colli posterior is the muscle which is excessively de- 

 veloped. It becomes differentiated from the posterior dorso-spinal 

 mass opposite the 14th and 15th cervical vertebrae to run up the 

 neck in the form of a fleshy belly which receives additional origins, 

 in the form of muscular slips, from the vertebrae as high as the 9th 

 cervical. Where the slip from the 10th vertebra (which is a small 

 one) joins it, the muscle becomes tendinous, forming a rounded cord, 

 to the inner side of which the large fasciculus from the 9th vertebra 

 is attached. 



A reference to the account given above of the disposition of the 

 vertebrae in this region will make it evident that the tendon of the 

 longus colli posterior must make a considerable backward turn op- 

 posite the transverse line of articulation between the 8th and 9th 

 cervicals — because there the two bones meet at a considerable angle, 

 with the genu directed forwards. This being the case, some special 

 mechanism is essential to prevent the tendon from breaking away 

 from the vertebral column when the muscle with which it is 



