HEAD-MUSOLES IN GALLUS AND OTHER SAUKOPSIDA. 511 



The Development of the Head-muscles in Gallus 



domestic us, and the Morphology of the 



Head-muscles in the Sauropsida. 



By 



F. H. Edg:ewoi-tli, M.S., D.Sc, 



Professor of Medicine, University College, Bristol (from the Anatomical 



Laboratory). 



With 39 Text-fiifures. 



/ A FEW papers have been published on the early stages of 

 development of the head-muscles of Gallus and other birds, 

 and on the insertion of the mandibular muscles into Meckel's 

 cartilage and the lower jaw; but as yet there has been no 

 description of the formation of all the muscles in any one bird 

 which might serve as a basis for a discussion of their morpho- 

 logy. The following is a contribution to the subject founded 

 on an investigation of Gallus. 



I found it was impossible to understand these head-muscles 

 without comparing them with those of Reptiles, but the diffi- 

 culty of doing so was accentuated by the almost complete 

 absence of knowledge of their development ; for although 

 Corning has described the early stages in Lacerta, the later 

 ones are not known, and no other Keptiles have been investi- 

 gated. Several friends, however, were good enough to lend 

 me sections or embryos of the later stages of Chelone, Alliga- 

 tor, Sphenodon, Agama, and Chamasleon, and I was able to 

 procure those of Tropidonotus natrix, so that it was 

 possible to follow the growth and changes in the muscles 

 which take place and give each group its special charac- 

 teristics. 



VOL. 5], PART 4. NEW SERIES. 39 



