INDIVIDUAL VARIATION IN EQUUS ASINUS. 721 
inferior part of internal surface of superior third of stylohyal, 
has often another one, quite distinct from the inferior third. 
We more frequently see the latter in the horse. 
Hyoideus parvus sometimes absent. 
Hyoglossus brevis sometimes attached to stylohyoid, generally 
not. 
Arytcenopharyngeus is occasionally well marked. 
Retractor oculi may form a complete investment of the optic 
nerve, or consist of four bands corresponding with the recti. 
The middle oblique muscle of the eye, as described by Strange¬ 
way s,;occasionally occurs in the ass. 
The inferior opening of the lachrymal ductus ad nasum varies 
in position; generally it opens at the upper part of the anterior 
naris, thus differing remarkably from the same structure in the 
horse. 
Neck.—Levator humeri never shows the fibrous band indica¬ 
tive of the seat of the clavicle, which this muscle has in the ox, 
pig, and other ungulates; but this information is conveyed in 
some subjects, in which we have seen a small muscle running 
from levator humeri around the anterior part of pectoralis 
anticus to the inner side of that muscle, where it disappears. 
Serratus magnus has sometimes a distinct rudimentary divi¬ 
sion passing to second cervical transverse process, generally only 
extends as far forwards as the third (see arrangement in ox). 
Scalenus: instead of terminating by each head at the first 
rib as in the horse, the superior division may be prolonged to 
the third rib or even further back, (see arrangement in ox) over 
serratus magnus. 
Longus colli we have seen attached only beneath the five 
anterior instead of the six anterior dorsal vertebrae. 
Back.—Transversalis costarum posteriorly in some cases is 
large and muscular and blended with longissimus dorsi in the 
lumbar region; in others it is tendinous and inserted into first 
umbar transverse process. 
Serratus posticus minor varies considerably in its development 
and attachments. 
Latissimus dorsi just before its insertion into the humerus 
varies in its relations with scapulo-ulnaris. Sometimes serial 
muscular bands beneath the arches of the ribs run from one rib 
to another, crossing two or three; these subcostales vary in 
number, are sometimes continuous posteriorly with the psose, 
and are covered by the pleuro-costalis. 
Transversalis abdominis varies in the degree of extension of its 
tendon towards the internal abdominal ring. The rectus abdo¬ 
minis has a variable number of transverse tendinous markings, 
