6i8 MUSCULAR SYSTEM 



Hitherto it has always been stated that Upupa has free tendons 

 (as in type VII.) and this has been used as an argument for placing 

 it among the Passeres ; but, as a matter of fact, in Upupa and Irrisor, 

 tendon P sends a vinculum to the slips of tendon A which goes to 

 iii., and this vinculum joins A below, not above, the root of the toes 

 (see fig. V,d). 



VIII. This type is peculiar to the Trogonidse. These Birds are 

 heterodactyl, the hallux and second toe being reversed, while the 

 third and fourth are front toes, and their deep flexor tendons like- 

 wise anomalous. Tendon A goes to the two hind toes i. and ii., 

 and by the vinculum together with tendon P to iii. and iv. 

 Analysis of this case means : fusion of P with A, without any 

 crossing; proximal splitting-off of the tendons for i. and ii. from 

 the tibial side of A ; and consequently direct derivation from type 

 V,a, analogous to, but more exaggerated than, V,b. 



These eight types are to be genetically grouped as follows : 

 I. II. III. IV. and VII. are closely allied to each other ; I. and IV. 

 to be derived from II. and VII. from I., while III. is a compara- 

 tively primary condition ; V, a shews a primitive stage, whence are 

 developed in diverging directions V,b, V,c, V,d, VI. and VII. 

 Any derivation of VI. from VIII. or vice versd is impossible ; and 

 the same applies to V, c and VI. 



B.a. Muscles of the Visceral Skeleton, which according 

 to their innervation, derivation and function fall naturally into 

 three groups. 



1. Group of the m. mylohyoideus, formed by the most anterior 

 continuation of the m. cucullaris and m. constrictor colli and consist- 

 ing of two portions: (1) m. mylohyoid. anterior, lying between 

 the branches of the mandible from the inner face of which its 

 transversely-directed fibres arise to meet in the middle line, and by 

 their contraction press the tongue and larynx against the palate, 

 and supplied from the third ramus of the nervus trigeminus, and 

 (2) m. mylohyoid. posterior, arising from the outer face of the 

 posterior end of the mandible and sometimes also from the adjoin- 

 ing part of the occiput, and inserted in the corner formed by the 

 hyoid horn and the corpus linguze, being supplied by a branch of the 

 nervus facialis, and drawing the tongue with the larynx upward 

 and backward. When the tongue is very protractile or very thick 

 this portion consists of two parts, one, m. serpi-hyoideus, arising 

 from the serpiform process of the mandible, the other, m. stylo- 

 hyoideus, from the occiput. 



2. Group of the masticatory muscles, supplied by nervus 

 trigeminus and n. facialis. 



M. digastricus or depressor mandibulse, large and often compound, 

 generally arising from the lateral occipital bone, and inserted on the 



