■« 



662 Dr. HARRIS H. WILDKR, 



Insertion. Like the preceding, into a tendinous raphe in the 

 median line. The raphe of both this and the previous muscle is liable 

 to variations, in some cases being almost wanting. 



This is undoubtedly the explanation of Fischer's statement. 

 „Nur in einigen Fällen {Hypochthon, Menopoma) bleibt zwischen den 

 Muskeln beider Seiten eine Art ,Linea alba', die zugleich an der Haut 

 befestigt ist" (J. 41). 



Innervation. From the Ramus jugularis facialis which is spread 

 over its surface. 



6. Gfenio-hyoideus (fig. ^gh). 



Preparation. By the removal of the two preceding muscles, 

 the genio-hyoideus is exposed throughout its entire extent, and appears 

 as a ribbon - like band on either side of the middle line , extending 

 from the symphysis of the jaw to the 2"'' basibranchial. External to 

 this, and extending posteriorly and laterally, are seen the lateral lobes 

 of the enormously developed thyroid gland, running upon which is seen 

 the hypoglossal nerve, which supplies this muscle. After observing 

 this nerve supply, the muscle may be divided across at its middle, 

 and either end reflexed. This will expose the entire thyroid gland, 

 which is best prepared at this stage of the dissection (vide infra 

 sub „Glandula thyroidea"). 



Origin and Insertion. This muscle arises from the internal 

 margin of the mandible, next to the symphysis, runs parallel to the 

 axis of the body, and is inserted in the terminal branching processes 

 of the 2"'' basibranchial. 



Innervation. The nerve supply, as given above, is from the 

 hypoglossal, which in this animal, as in all Amphibians, is not yet a 

 cranial nerve, but formed by the 1'' and 2"'* cervical. 



7. Cerato-hyoideus externus (figs. 1, 4 ce). 



Preparation. This, the largest of the muscles now exposed, 

 extends between the cerato-hyale and the epibranchiale 1, curving 

 diagonally from a median anterior to a lateral posterior position. 



The investing fascia should first be removed and then the location 

 and relations of the muscle carefully studied, by drawing apart the 

 different skeletal elements without cutting N. hypoglossus. 



In the interspace between the mandible and the ceratohyal, and 

 resting upon the lower surface of the mucous membrane of the mouth, 

 runs a fine nerve which supplies the upper portion of the muscle iu 



