11 
Mammals generally. 
Orbicularis-oculi-group. M. maxillo-labialis. 
12 
principally transverse, but at the upper end they expand like a 
fan, the posterior fibres extending above the eye. In the other 
Mammals which have been closer examined the muscle was 
found to have become separated into several muscles. 
Firstly most of the fibres in front of the eye have been di¬ 
vided transversely by the anterior palpebral ligament; the prse- 
orbicularis being thus separated into a prceorbicularis dorsalis and 
venlralis; sometimes however some bundles go from one into the 
other (Horse, PI. 16, fig. 26). From the palpebral ligament the 
fibres of these muscles extend respectively dorsad and ventrad, 
close to the orbicularis proper, being a direct continuation of 
this; the fibres having principally a transverse direction, gene¬ 
rally spreading like a fan respectively dorsally and ventrally. 
Posteriorly the prseorbicularis dorsalis may be continued into a 
m. supraorbicularis, which sometimes (Elk, Camel, Swine, PI. 16, 
fig. 22, 21, 25) is a direct caudad continuation of the prseorbicu- 
laris dorsalis; the fibres have a similar direction like the posterior 
fibres of the prseorbicularis dorsalis, viz. oblique, the lower ends, 
which are attached to the orbicularis, being foremost. In other 
cases the supraorbicularis has been more completely differentiated 
from the rest of the prseorbicularis dorsalis; in the Horse (PI. 16, 
fig. 26) for instance it has become rather sharply separated, and 
in the Tapir (fig. 27) it has become displaced so as to take place 
inside the prseorbicularis. The same is also the case in Bos (fig. 23), 
where the supraorbicularis has assumed an extraordinary develop¬ 
ment, extending backward over the whole frontal plane, the di¬ 
rection of the fibres posteriorly being longitudinal. 
The prceorbicularis ventralis is in some forms feebly deve¬ 
loped (Didelphys, Centetes, fig. A, B), in others it is a rather large 
muscle (e. g. Bos, PL 16, fig. 23). In Alces (fig. 22) it is very large 
and divided into two portions, a hind portion fpru 2) behaving 
as usual, and a front portion (prv 1J arising from the lacrymal 
bone and extending downwards like a fan; it is covered partially 
by the first-named portion, with which it is intimately connected. 
From the prseorbicularis is also derived the m. nasolabialis 
(PI. 17, fig. 1). In Echidna it is not yet separate from the prse¬ 
orbicularis, with which it is also intimately connected in several 
of the others. The fibres of this muscle have generally an oblique 
direction, the ventral ends, which extend into the upper lip and 
unto the nares, being foremost. Originally (Didelphys, fig. A; Cen¬ 
tetes, fig. B; Prosimise) the muscle extends a way above the eye; 
and in Centetes this is so far exaggerated, that the muscle ex¬ 
tends posteriorly above the ear and further on (this is probably 
a consequence of the existence of the spinous coat of this ani¬ 
mal). But often, as is the case with all the Ungulata examined, 
the part of the muscle extending above the eye is very little de¬ 
veloped. The nasolabialis is generally a muscle of considerable 
strength, extending often over a large part of the face. In some 
forms, e. g. the Camel (PI. 5), there is no limit whatever between 
the nasolabialis and the prseorbicularis, the former being a direct 
rostrad continuation of the latter, especially of the prseorbicularis 
ventralis; in other forms, as the Tapir (PI. 16, fig. 27; PI. 7), it is 
more, but not quite, independent, the caudal fibres still being 
closely attached to the front margin of the prseorbicularis ven¬ 
tralis. In the Horse (PI. 16, fig. 26) it is still more independent, 
and in the Swine (PI. 9) it has been widely separated from the 
prseorbicularis through a broad space. — The Elk presents the 
peculiarity, that the right and the left nasolabialis unite above 
the snout and here form a layer of transverse fibres. 
The Wapiti (PI. 16, fig. 24) and the Zebu (fig. 23) are peculiar 
in that a smaller or greater number of the dorsal ends of the 
fibres of the prseorbicularis dorsalis turn in a bow, into the 
nasolabialis, and are continued in the same direction as the 
fibres of the nasolabialis, forming a smaller or greater part of 
this muscle. The arrangement is such, that if no other Mammals 
were known than the Wapiti and Zebu the natural inference of 
the facts would be, that the nasolabialis had been derived from 
the prseorbicularis dorsalis in such a manner, that the rostral 
fibres of the latter had grown down in a bow into the upper 
lip — an inference which the comparison with other Mammals 
shows to be erroneous. 
Generally, the muscle has no definite origin from the bones 
of the face. But in Nasua (PI. 11, fig. 2) where the inferior ends 
thereof are inserted into the tendons of m. maxillo-labialis, and 
into this muscle itself, it takes a definite origin from the skull 
in front of the eye, and is here intimately attached to the bone. 
That it has been developed in this manner in Nasua is probably 
a consequence of the development of a moveable proboscis in 
Nasua; the m. nasolabialis has assumed the part of an auxiliary 
of the m. maxillo-labialis — the principal motor of the proboscis — 
and must therefore have a fixed origin. In the Dog, where the 
inferior ends of the nasolabialis are also inserted into the max¬ 
illo-labialis, it does not take its origin from the bone but extends 
in the usual manner in front of the eye loosely connected with 
the underlying parts. 
3. MUSCULUS MAXILLO-LABIALIS. 
The m. maxillo-labialis (PL 17, fig. 3), which is covered by 
the nasolabialis, appears as quite independent from this and 
from the other facial muscles; the connection with the scaninus- 
orbicularis« (front part of sphincter prof.), which Ruge has found 
in the Prosimise, we have not found in the forms examined by 
us, and we can only regard that connection in the Prosimise as 
a quite secondary. The muscle takes its origin below, behind 
and above the foramen infraorbitale and extends into the upper 
lip and round the external nares. The direction of its fibres is 
mainly a horizontal one. At the origin the muscle is generally 
fleshy, but it may sometimes arise with shorter or longer tendi¬ 
nous parts. At the other end it generally terminates in several 
tendons, but parts of it maj' also terminate fleshy. 
The muscle has a distinct tendency to separate into several 
portions. More especially we find a very general tendency for 
this muscle to split into an upper part — the portio superior 
nobis — and a lower part — the portio inferior. In Alces (PL 11, fig. 1) 
the portio superior is still coherent with the rest of the muscle, but 
the fibres and tendon thereof have another direction than the rest, 
which direction is oblique, and upward; the numerous branches 
in which its tendon is ultimately split up, end on the upper side 
of the nose. In the Horse (PL 8, fig. 1) and the Tapir (PL 8, fig. 2) 
the portio superior (the m. levator labii superioris proprius of 
the Veterinarians) has been entirely separated from the rest 
through a large interstice, and ultimately it is united with that 
of the other side and ends at the front end of the proboscis (in 
the Tapir) or in the upper lip (Horse). — In the Camel (PL 11, 
fig. 4) the portio superior has quite disappeared, the maxillo-la¬ 
bialis consisting only of the bundles arising below the foramen 
infraorbitale (comp, the figure of the Camel and those of the Tapir 
and the Horse). 
The relation of the maxillo-labialis of Centetes to that of 
Erinaceus is similar to that of the same muscle in Alces on one 
side and in the Horse on the other. In Centetes (fig. C) the por¬ 
tio superior is still united with the rest, but on the way to se¬ 
paration. In Erinaceus (PL 11, fig. 3) the portio superior is quite 
separate (but still borders on the portio inferior) and very large, 
arising from the front margin of the orbit, above and below the 
entrance to the lacrymal canal; its long tendon joins — as is 
also the case with Centetes — that of the other side above the 
nasal cartilage and the common tendon is inserted into the skin 
of the dorsal side of the tip of the nose. The portio inferior 
arises in Erinaceus from the zygoma and is divided into four 
parts which are rather deeply separated. The three superior are 
each continued into a long tendon, which, as the corresponding 
tendons in Centetes, end in the skin on the side of the nose; 
the fourth, the inferior, ends fleshy in the upper lip. 
In the Dog (PL 12) there is also an upper and a lower por¬ 
tion, which are quite separated throughout their whole extent; 
they both arise contiguously below (and behind) the foramen 
infraorbitale; into the upper margin of the lower portion the in¬ 
ferior ends of the m. nasolabialis are inserted. Towards its an¬ 
terior end the upper portion is split up into numerous fine ten¬ 
dons terminating behind the external nares, while the anterior 
ends of the lower portion are fleshy throughout. — In Nasua 
(PL 11, fig. 2) the muscle is far stronger than in the Dog, and its 
