108 
PROFESSOR WOOD OX THE NECIv- AND SHOULDER-MUSCLES. 
to be made up chiefly by the union, at the imperfect clavicle or its tendinous represen- 
tative, of a sterno-clavicular and a s c ap ulo-clav i cular element. 
In the heavier animals, in whom the clavicle is altogether wanting, it constitutes a 
continuous muscular support to the trunk upon and between the scapula;, uninterrupted 
by the intervention of a clavicular representative, and embodying all the various elements. 
In animals possessed of a clavicle, and using the fore paws as hands, the distinction 
of the sterno-clavicular , subclavian , and scapulo-clavicular elements becomes more 
marked ; while in some, like the Rabbit, a combination of all these is evident in the 
compound muscular mass. In the Guinea-pig the sterno-clavicular and scapulo-clavicular 
are large and distinct muscles, while the sterno-scapular is also very distinct and separate 
from them. In the Norway Rat the subclavius and sterno-scapular are distinct, and the 
scapulo-clavicular well marked, while the sterno-clavicular seems altogether wanting. 
The last-named element seems to be the most marked in Mammalia of burrowing and 
flying habits, and it draws powerfully the primary segment of the fore limbs, chiefly 
used in these motions, backwards against the resisting and reacting atmosphere. All 
these modifications are evidences of teleological adaptations of a common morphological 
structure, such as we find prevailing in other parts of the animal organization. 
Supracostal Muscle. — An abnormal and infrequent variety in the human subject was 
first recorded and described by me in the ‘Proceedings of the Royal Society’ of 1865. 
It occurred, on both sides, in a muscular male subject, in whom a levator-claviculce and 
thirteen other abnormalities were found (see Plate IX. fig. 8, n). It was a thin, flat, 
ribbon-shaped muscle, placed upon the upper four ribs, between the digitations of the 
pectoralis minor and those of the serratus magnus. It was attached above to the outer 
edge of the first rib near its cartilage, by a fleshy attachment about an inch broad, 
passing downwards and slightly forwards ; the fibres gradually spread out in somewhat 
of a fan-shape, and dropped insertions into the outer surfaces of the second, third, and 
fourth ribs, close to the origin of the pectoralis minor. It was entirely distinct from 
the intercostals, from which a well-marked fascia separated it. 
In the ‘ Proceedings of the Royal Society ’ of 1867 I recorded another specimen, found 
also in a male subject, and on both sides. It was attached above to the first rib, as in 
the first case, and was connected also externally to the cervical fascia covering the sca- 
lenus anticus, with which it seemed to be in part continuous. Below it was attached to 
the third rib only, in front of the serratus magnus. Since that time we have found 
another specimen of this muscle, also in a male, and on both sides. 
Mr. Macalister has found this muscle several times, very large and muscular. In a 
male subject it existed on the left side only, attached above wholly to the cervical fascia, 
and below to the third and fourth ribs, about 6-| inches from the sternum, in the same 
situation as the foregoing. He has found it usually narrower and thicker on the right 
side than on the left. In one instance it measured 3f inches long, f inch wide, and -g- inch 
thick, overlapping the upper digitations of the serratus magnus , and ascending behind 
the axillary vein, was attached on the right side to the first rib, and on the left into the 
