1897.] NEW YORK ACADEMY OF SCIENCES. 91 



and passes to the tongue muscles without attachment to the 

 H3'oid bone. 



Fewkes describes tliis muscle under the name of Sterno-glossus. 

 Its homology with the usual mammalian Sterno-hyoid appears 

 from the absence of a regular Sterno-hj^oid and from the nerve- 

 supply by branches from the upper cervical nerves through the 

 Hypoglossal. A partial or complete replacement of the usual 

 Sterno-hyoid by a Sterno-glossus, passing over the Hj'oid bone, 

 and joining the muscles at the base of the tongue, is noted in 

 Myrmecaphaga, Manis and Dasypus. 



In some forms {Phascolarctos) the muscle is attached to the 

 median surface of the Inferior Maxilla — forming a Sterno-maxil- 

 laris (Owen, Ponchet, Macalister). 



McWhinnie describes in man aberrant fascicles of the muscle 

 as passing over the Hyoid bone to join the Mylo-hyoid, and the 

 partial union of the Sterno-hyoid and Sterno-thyroid with the 

 Hyoglossus is very frequent. 



The frequent connection between Sterno-thyroid and Thyro- 

 hyoid, present in many mammalia as the typical condition,* 

 shows conclusively that the two muscles are to be regarded as a 

 single morphological unit, which has undergone a division into 

 two segments by contracting an intermediate adhesion to the 

 Thyroid cartilage. In man the muscle in addition appears 

 united by variation with the Sterno-hyoid, Omo-hyoid and Hyo- 

 glossus (Walsham). Gegenbaur's investigations show that the 

 Omo hyoid is a part of the muscle group which in Man is still 

 represented b^' the Sterno-hyoid and Sterno-th^oid, but which in 

 earlier types extends from the sternal region over the Clavicle 

 and proceeds thence to the Scapula. 



Union with the Sterno-h3'oid is noted in man as a variation and 

 the extension of the muscle into the supra-h3'oid region is noted 

 by Macalister, who found some fasciculi passing to the Mylo- 

 hyoid, after having passed over the Hyoid bone, and by Wood, 

 who notes partial union with the Stylo-h^oid. 



In Ornithorhynchus the muscle is double, one part passing 

 into the Hyoid, another inserting into the Inferior Maxilla. 



From the facts just cited — and similar evidence could readily 

 be multiplied — the morphological unity of the hyoid group of 

 muscles is apparent. Moreover the extension of the infra-h3'oid 

 division of this group into the h3^o-maxillar3' region and into the 

 tongue, as noted in the above instances, appears to mark the 

 earlier condition of the muscular plane, before secondaiy attach- 



*Lutra, Phoca, Hapale, Cebus. Cynocephalus, Troglodytes, Gorilla exhibit the 

 union very weU ; less closely connected are the two muscles in Man, Hystric, Viverra, 

 Metes and Macacus. 



