598 
F. H. EDGEWORTH. 
persisting distal portion becomes attached to the tensor veli 
palatini by tendon. 
In the pig such a proximal portion is not formed ; only the 
persisting distal portion, behind the Anlage of the tensor veli 
palatini, is developed, as found by Eschweiler. All trace is 
thus lost, even in developmental stages, of the ancient origin 
from the pterygoid bone. 
It may be concluded, from the descriptions given by 
Znckerkandl, Kostanecki, Schnlman, and Eschweiler, that the 
tensor tympani does not arise from the (Mammalian) pterygoid 
bone in any adult mammal. This may be due to loss of such 
attachment during development, e. g. in Echidna, Dasyurus, 
Bradypus marmoratus, or to its non-formation, e . g . rabbit 
and pig. 
Disappearance of the proximal portion of the muscle either 
by ontogenetic atrophy or by non-formation is a marked 
characteristic of the muscle. In the former case it is apparently 
brought about by the bulging wall of the pars cochlearis of the 
auditory capsule interrupting the line of action of the muscle. 
/ The proximal end of the persisting, or solely developed, 
distal portion of the muscle gains secondary attachments, and 
especially to the pars cochlearis of the auditory capsule and 
Eustachian tube. Of these attachments that to the Eustachian 
tube is in close association with the secondary insertion of the 
tensor veli palatini, as described above. 
Eschweiler was of the opinion that these various attach- 
ments of the tensor tympani are derived from the condition 
found in Oruithoi-hynchus, where the muscle in the adult 
consists of two parts, both inserted into the malleus — a 
Eachenbauch which takes origin from ^Mer Muskulatur 
hervor welche am hintern lateralen Choanenwand entspringt,^’ 
and a Felseubeinbauch springing from the labyrinth wall. 
'The development of the muscle in Ornithorhychus is not 
yet known, but comparison with Ecliidna, Dasyurus, pig and 
rabbit leads to the conclusion that in all probability the 
“ Eachenbauch of Ornithorhynchus is a secondary forma- 
tion. 
