352 MALL. [VoL. XIV. 
tion, which shows its origin; that it is segmented is due to the 
ribs, a mechanical element. 
While in the sharks it is comparatively easy to follow the 
development of the eye muscles with their respective nerve 
connections, it is impossible at present to follow them in higher 
animals. The same applies to the muscles arising from the 
hyoid arch and innervated by the seventh nerve. It is a remark- 
able fact, however, as emphasized by Rabl, that just those 
muscles which belong to the hyoid arch are innervated in man 
by the seventh nerve. Even where we can see no sharp line 
whatever in the embryo, there is one which has been indicated 
to us by the study of sharks. Rabl? states, after speaking of 
the muscles of mastication: “ Die iibrige Gesichtsmuskulatur 
dagegen wird vom Facialis innerviert und sie ist, wie Gegenbaur 
und Ruge auf vergleichend-anatomischem Wege gezeigt haben, 
aus einer Differenzierung des Platysma hervorgegangen; das 
Platysma selbst aber gehort genetisch dem Hyoidbogen an und 
wird daher, wie seine Differenzierungsprodukte, vom Facialis 
versorgt. Ebenso scharf sondern sich auch die beiden Inner- 
vationsgebiete in der Paukenhohle. Hammer und Amboss 
entwickeln sich aus dem ersten, der Steigbiigel, wie ich ausein- 
andergesetzt habe, aus dem zweiten Kiemenbogen; der Muskel 
des Steigbiigels vom Facialis innerviert. Der Musc. tensor 
tymp. gehort mit dem Tensor veli palatini genetisch und 
anatomisch zu einer Gruppe (Schwalbe); der Musc. stape- 
dius bildet in ahnlicher Weise aller Wahrscheinlichkeit nach 
mit dem Stylohyoideus und hinteren Biventerbauch eine 
Gruppe.’ 
The short muscles of the trunk are innervated by single 
nerves, and in them the embryonic condition is retained. But 
in the case of the shifting of a muscle its nerve supply is not 
so simple as in case of the diaphragm. In this extreme example 
the muscle wanders down with the development of the septum 
1 Rabl, Avzat. Anz., Bd. ii, p. 226. 
1 There is a very extensive literature to show that the muscles of the limbs arise 
from the myotomes. The systematic work of Mollier (Anat. Hefte, No. viii) is one 
of the best of this group of papers. In my discussion above I have only brought 
forth some general objections to the views of Paterson and the much stronger and 
better arguments of Harrison. 
