THE MANDIBULAR AND HVOID MUSCLES OF MAMMALS. 597 
The distal end of the tensor veli palatini also gains attach- 
ment to the walls of the Eustachian tube, with which it is from 
the very first in close relationship. 
As regards innervation, Schulman determined that the 
])terygo-spinosus of Ornithorhynchus is innervated by a 
branch of the ramus medialis, s. ventralis, of the mandibular 
division of the fifth. Lubosch did not describe the innerva- 
tion of the pterygo-tympanicus of Edentates; but in Echidna, 
Dasypus novemcincta, Bradypus marmoratus, and 
Manis pentadactyl a, I found the same innervation as in 
Ornithorhynchus. 
The tensor veli palatini has long been recognised as being- 
innervated by the ramus medialis of the mandibular division 
of the fifth. I have recently confirmed this by showing that 
in Macacus cynomolgus the muscle degenerates after 
section of the fifth nerve proximal to the Gasserian 
ganglion. 
_Tensor Ty mpani. — The tensor tympani in early stages of 
Dasyurus passes from the pterygoid bone to the side of the 
body of the malleus portion of Meckebs cartilag-e. Later on 
the proximal portion of the muscle disappears, and the proximal 
end of the persisting distal portion becomes attached to the 
distal end of the tensor veli palatini and the cartilaginous wall 
of the auditory capsule. It may be inferred that a stage has 
been passed over in which the tensor tympani — as a separate 
muscle — arose from the ala temporalis. Such a stage is 
present in a 30 mm., i.e. relatively late embryo of Dasypus 
novemcincta. 
In Echidna, in stage 50, the tensor tympani passes from 
the (Mammalian) pterygoid bone to the malleus. The proximal 
portion of the muscle subsequently disappears, the proximal 
end of the persisting distal portion being- attached in the adult 
to the petrous bone (Eschweiler) . 
In the rabbit the muscle never has any origin from either 
theala temporalis or the pter^^goid bone, though a subsequently 
atrophying, proximal portion of the muscle, overlapping the 
tensor veli palatini, is formed. The proximal end of the 
