Henry L. Bruner 93 
Ill. THE SWELL MECHANISM OF THE TESTUDINATA. 
A. THE MUSCULUS CONSTRICTOR VENA JUGULARIS INTERNA®. 
In the Testudinata the swell mechanism of the head includes a m. 
constrictor vene jugularis interne, which shows a strong and peculiar 
development. In Emys europea the muscle begins directly behind 
the Eustachian tube and accompanies the vena jugularis interna under 
NSMss we : ike 
A i\ Pa 
mc.cl 
Fic. 16. Transverse section of Emys europea, through the anterior part 
of the m. constrictor vene jugularis interne. xX 13. The section passes 
just behind the jugular foramen. 
m. c. j. 7., m. constrictor vene jugularis interne, anterior portion; m. d. t., 
m. dilatator tube; Ol., occipitale laterale of cranial wall; Ol’., occipitale later- 
ale of parotic region; 7. m. a@., ramus muscularis anterior of vago-accessorius 
(for m. c. 7. 1. and m. d. t.); v. c. p., vena cerebralis posterior; v. 7. i, vena 
jugularis interna; JXg., ganglion glossopharyngei; Xg., ganglion superius 
vagi. 
Other muscles represented are: m. a. e. 0., m. atlanto-epistropheo-occipit- 
alis; m. a. 0., m. atlanto-occipitis; m. c. c. l., m. collo-capitis longus; m. c. m., 
m. cerato-maxillaris. 
the floor of the tympanum and into the neck. The anterior half of 
the muscle (m. c. 7. 1., Text Fig. 16) is composed chiefly of fibers which 
form loops below the vein, one arm of the loops lying median, the other 
lateral to the vein. The ends of these fibers are attached to the floor 
of the tympanic cavity above the vein. Some of these loops lie in a trans- 
verse plane but the majority are oblique, the median attachment being 
more posterior than the lateral attachment. This arrangement explains 
