Henry L. Bruner 95 
end (m. d. t., Text Fig. 16) lies lateral to the vena jugularis interna, 
while its anterior end is inserted on the wall of the Eustachian tube di- 
rectly ventral to the vein. In some cases the two muscles are not wholly 
separate, as fibers pass from one muscle to the other. The two muscles 
also receive their nerve supply from a common trunk. In view of its 
close relation to the constrictor muscle and to the vein it is possible that 
the m. dilatator tube may assist in obstructing the vena jugularis interna. 
The constrictor muscle of the turtle is innervated by branches of a 
nerve which I designate ramus muscularis anterior vagi (7. m. a., Text 
Fig. 16). This nerve arises from the anterior lateral portion of the 
ganglion radicis vagi, which hes median to the anterior part of the con- 
strictor muscle. Near its origin the nerve divides into two unequal 
branches, the smaller of which, nervus tumefactor capitis posterior, bends 
directly caudad to enter the posterior part of the constrictor muscle. 
The larger nerve turns forward and divides again, one branch entering 
the m. dilatator tube, while the other, nervus tumefactor capitis anterior, 
supplies the anterior part of the constrictor muscle. 
I have not attempted to determine definitely whether the fibers of the 
nervi tumefactores capitis belong to the vagus or to the accessorius. The 
roots of the two latter nerves form a close series and it is impossible to 
draw a line between them. By electrical stimulation of the roots in 
Cistudo carolina it has been found, however, that the fibers of the tume- 
factor nerves pass through the anterior members of the series; hence, they 
probably belong to the vagus of authors. 
In addition to the forms mentioned, the m. constrictor venee jugularis 
interne has been demonstrated microscopically in the following species: 
Kinosternon pennsylvanicum Gmelin. 
Aromochelys odorata Bose. 
Aspidonectes spinifer LeSeur. 
Tn all of these the constrictor muscle shows practically the same de- 
velopment as in Emys. The m. dilatator tube is also present and closely 
related to the constrictor muscle. 
B. DISTENSION OF THE VEINS AND SINUSES OF THE TESTUDINATA. 
The flooding of the cephalic veins and sinuses under natural condi- 
tions has not been observed in the Testudinata. The following experi- 
ments on the American speckled tortoise, Clemys guttata Schneider, are 
important, therefore, as indicating the probable nature and significance 
of the process: 
Two small pieces of court plaster were applied to the left orbital 
