THE MUSCULAR SYSTEM 



199 





i|i^ ^^^--^ FiM-rniX"^ MYOTOMIC buds' \ ^'^-"-^ h, 



FIN-FOLD 



"•" "Sypogldssus muscle buds 



B. 



\ COELOM,/;- 



Fig. 188. — Diagram of bvidding of hypoglossal and pectoral fin muscles from 

 trunk myotomes in an elasmobranch embryo. A. Lateral view after Braus. 2-6, 

 visceral arches. B. Cross section in region of pectoral fin-fold. 



LEVATORES ARCUORUM C(-7) 



VISCERAL SKELETAL ARCHES Cl-7) \ 



DEPRESSORES ARCUORUM Cl-7^ 



LEVATORES [-4 



DIGASTRICUS 

 MASSETER 

 TEMPORALIS 



DORSO-LARYNGIS AND 

 DORSO- TRACHEALIS 



B. 



INTERMANDIBULARES 



HYO-PHARYNGEI 



Fig. 189. — Diagrams illustrating the hypothetical evolution of the branchiomeric 

 muscles. A. Hypothetical ancestral form. B. Branchiomeric muscles in urodele 

 amphibian. (Redrawn after Wilder's "History of the Human Body," Henry Holt 

 & Co.) 



