THE MANDIBULAR AND HYOID MUSCLES OF MAMMA I. S. 607 
muscles only: ;i medial arising from the ala temporalis and 
inserted into Meckehs cartilage and innervated by the I’amiis 
medialis of the mandibular division of the fifth nerve, and a 
lateral arising from the orbito-parietal commissure and 
inserted into a rudimentary mandible and innervated by the 
ramus lateralis. 
In Sauropsida^ the Anlage of the masticatory muscles divides 
into upper and lower portions, the former inserted into the 
palatine process of the quadrate, the latter extending from 
the palatine process of the quadrate to Meckehs cartilage. 
The upper portion forms the spheno-pterygo-quadratus or a 
homologueof this muscle, or — as in Cheloniaand Crocodilia — 
atrophies. The lower portion of the Anlage of the mastica- 
tory muscles separates into inner and outer parts, the inner 
developing into the pterygoid muscle or muscles, and the 
outer into the capiti-rnandibularis. The dorsal end of the 
capiti-mandibularis, at first attached to the palato-quadrate, 
grows upwards and gains a dorsal attachment to the 
skull. 
Thus, whilst in Mammals the AAlage of the masticatory 
muscles does not divide into upper and lower portions, in 
Sauropsida it does so. This cardinal difference is not taken 
into account by Fiirbringer, Kostanecki, Gaupp, and Cords, so 
that the various homologies which they regard as existing 
between individual masticatory muscles in these two great 
Vertebrate groups are questionable. 
In Amphibia the Anlage of the masticatory muscle does not 
divide into upper and lower portions, above and below the 
palatine process of the quadrate. The whole dorso-ventral 
strip separates into a medial and a lateral muscle. 
The initial stages of development of the masticatory 
muscles in Mammals are thus exactly comparable to those of 
^ Only the barest outline of the phenomena is stated here. In the 
‘ Quarterly Journal of Microscopical Science,’ vol. 51, 1907, I gave a 
short account, in all groups of the Sauropsida, with an analysis of the 
somewhat bewildering array of names given to the muscles by various 
observers. 
