112 PHYSIOLOGICAL SEKIES. 



muscles. The two bellies of the depressor are separated, as 

 in the Guinea-pig, by a constriction and superficial central 

 tendon. A fine tendon connects the latter with the 

 posterior margin of the mylohyoid. The intermundibular 

 space close behind the symphysis is occupied by an inde- 

 pendent portion of the mylohyoid (transversus mandibulse) : 

 its contraction divaricates the lower incisors. 



C. 103. Head of a Fox-Squirrel (tic'ntrus ludovicianus), showing, 

 from the ventral aspect, the depressor maxillse inferioris 

 (digastric) muscles. They are strongly digastric ; the 

 central tendons have an attachment to the hyoid, and by 

 union with one another in the mid-line form a sub-hyoidean 

 tendinous arch, from the anterior margin of which the 

 anterior bellies arise. The latter are closely contiguous and 

 occupy the median third of the intermandibular space. 

 They are inserted at the symphysis menti. 0. C. 64 z I a. 

 Parsons, Jour. Anat. & Phys., vol. xxxii. 1898, p. 438. 



C. 104. Part of the skull and hyoid bone of a Colt (Equm 

 caballus) showing the depressor maxilla? inferioris (digas- 

 tric) and stylohyoid muscles. The depressor is strongly 

 digastric ; its long central tendon perforates the tendon of 

 attachment of the stylohyoid. A large part of its posterior 

 belly is attached directly to the inner surface of the angle 

 of the mandible. The stylohyoid is divided into two 

 portions by the posterior process of the stylohyal. The 

 proximal part (mastoideo-styloideus) regarded by some 

 as part of the depressor passes from the paroccipital 

 process to the stylohyal. The distal part rises by a slender 

 tendon from the outer surface of the posterior process of 

 the stylohyal. Presented by Prof. McFadyean. 



C. 105. Occiput, hyoid, and lower jaw of a Sheep (Ovis arles], 

 showing the depressor maxilla 1 inferioris (digastric), stylo- 

 hyoid, mylohyoid, and hyo-epiglottidean muscles. The 

 depressor is a strongly digastric muscle with its anterior 

 belly attached far back upon the inner surface of the 

 mandible and partly also into the mylohyoid. The mas- 

 toideo-styloideus is fan-shaped : the stylohyoideus rises 



