618 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 Zrogonidx. '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 i. 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. II. 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 lingux, 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 mandibulx, large and often compound, 
generally arising from the lateral occipital bone, and inserted on the 
