The Thoracic Limb of the Horse 2.
The Thoracic Limb of the Horse 1 deals with extrinsic muscles of the forelimb, the
muscles that extend from the axial skeleton to the limb. With this presentation, we
deal with intrinsic muscles of the forelimb, muscles that extend between bones of the
limb. We treat here initially, the muscles that extend between the scapula and
humerus, between the scapula and the radius and ulna of the forearm, and between
the humerus and bones of the forearm. These muscles act on the shoulder and elbow
joints.
The formal name of the shoulder joint is the humeral joint but it is often, and more
precisely, designated the scapulohumeral joint. Sometimes, owing to the fact that it is
formed by the glenoid cavity of the scapula and the head of the humerus, it is
designated the glenohumeral joint. The elbow joint is a joint between three bones:
humerus, radius, and ulna. It is comprised of humeroradial and humeroulnar joints.
The formal name of the elbow joint is the cubital joint.
The shoulder joint is formed by the articular surfaces of the glenoid cavity of the
scapula and the head of the humerus. The glenoid cavity, a shallow concavity, is
much smaller than the head of the humerus, which is large and hemispherical, larger
than the head of the femur. The hemispherical shape of these articular surfaces tells
us that all movements are possible at this joint: extension, flexion, abduction,
adduction, and circumduction. These movements are extensive at this joint and the
joint capsule is necessarily large to permit them. In flexion, the excess capsule will
appear caudally as a ventral saclike extension. This is significant, for example, in the
dog with osteochondritis dissecans as it is the place where osteochondral fragments
accumulate and are most easily surgically recovered.
The scapula is an endochondral bone and was initially laid down as a cartilage-model.
Ossification centers are formed 1) in the cranial part of the glenoid cavity before or at
the time of birth, 2) in the body of the bone at 2 to 2 ½ months postpartum, 3) in the
supraglenoid tubercle and coracoid process at 140 - 170 days, and 4) near the
attached margin of the scapular cartilage at 9 – 12 months. Fusion of centers 1 – 3
takes place by 9 – 18 months; but the scapular cartilage, which is the supplemented
original cartilage, remains largely cartilaginous throughout life. Its ossification center
joins the vertebral margin of the scapula only in older animals. These dates are taken
from Sisson and Grossman’s The Anatomy of the Domestic Animals, Vol. 1, Getty,
Ed.; Saunders:1975; 271-272;.
scapular cartilage
trapezius,
thoracic part;
deltoideus
trapezius,
cervical part
teres major facet
infraspinous fossa
teres major
tuber spinae
supraspinous fossa
supraspinatus
scapular spine
scapular notch
triceps
brachii
Infraspinatus b
neck
biceps
brachii
supraglenoid tubercle
Fig. 1a. L scapula, lateral view, with
named prominences and
depressions. Figure is from Sisson.
Fig. 1c. Intrinsic
shoulder muscles
(deltoideus
removed). Lat. view.
Drawn by David
Stewart Geary.
teres
minor
Infraspinatus a
aa
Fig. 1b. L scapula, lateral view.
Areas of muscular attachment are
marked. Figure is from Sisson.
supraspinatus
teres major
infraspinatus
triceps brachii
teres minor
tensor fasciae antebrachii
(attaches to scap w/triceps)
biceps brachii
Fig. 2. Shoulder muscles, lat. vw.
Drawn by David Stewart Geary.
trapezius
latissimus
dorsi
omotransversarius
deltoideus
brachiocephalicus
tensor fasciae
antebrachii
triceps
brachii
Main attachments of intrinsic muscles to the scapula proximally and to the humerus,
or to the radius and large metacarpal bone (MCIII), distally:
Supraspinatus: Supraspinous fossa of scapula to the cranial prominence of the
greater and lesser tubercles of the humerus.
Infraspinatus: Infraspinous fossa of scapula to infraspinatus facies of humerus
(Infraspinatus a) and, from the ventral part of the fossa, to the caudal prominence of
the greater tubercle of the humerus (infraspinatus b).
Deltoideus: Scapular spine and proximal scapula to the deltoid tuberosity.
Teres minor: Muscular lines and surface in the ventrocaudal part of the
infraspinous fossa to the teres minor tubercle of the humerus.
Teres major: From a facet at the caudodorsal angle of the scapula to the teres
major tuberosity of the humerus. This muscle passes medial to the long head of
triceps to reach the teres major tuberosity on the medial side of the body of the
humerus.
Triceps brachii: Caudal margin of scapula (long head), line of triceps (lateral
head), and medial aspect of the humerus caudal to the teres major tuberosity (medial
head) to the summit of the olecranon of the ulna.
Tensor fasciae antebrachii: Dorsal part of the caudal margin of the scapula
with the long head of the triceps brachii and insertion tendon of the latissimus dorsi to
the medial surface of the olecranon and the medial forearm fascia.
Subscapularis: Subscapular fossa to the caudal prominence of the lesser
tubercle of the humerus.
Biceps brachii: Supraglenoid tubercle to the radial tuberosity of the radius and,
by the lacertus fibrosus, to the metacarpal tuberosity of MCIII.
Coracobrachialis: Coracoid process of the supraglenoid tubercle to
craniomedial surface of the shaft of the humerus.
Fig. 3. Shoulder muscles, medial
view. Modified from Sisson.
subscapularis
latissimus dorsi
subclavius
teres major
triceps brachii,
long head
medial head
supraspinatus
tensor fasciae
antebrachii
deep pectoral
coracobrachialis
biceps brachii
brachhii
deep fascia
Fig. 4. L scapula,
med. view, with
named prominenes,
surfaces, and
depressions. Figure is
scapular cartilage
facies serrata,
cranial facet
facies serrata,
caudal facet
subscapular fossa
Fig. 5. L scapula, medial
view, showing areas of
muscle attachment.
rhomboideus thoracis
supraglenoid tubercle
coracoid process
rhomboideus cervicis
teres major
serratus ventralis cervicis
serratus ventralis thoracis
subscapularis
triceps brachii
biceps brachii
Function of these intrinsic muscles on the humeral (scapulohumeral)
coracobrachialisjoint:
Muscle action. Striated muscle fibers can contract to about half their length.
Skeletal muscles are defined by their attachments. In contracting, all act only to
approximate their attachments. The result is that, depending on their attachments,
muscles seldom have a single action. For example, the teres major acts chiefly to flex
the shoulder joint but, owing to its passing to the teres major tuberosity on the medial
side of the humerus, tends also to adduct the limb. Likewise, muscles that attach on
the lateral side of the humerus tend to abduct the limb, and this is a chief action of the
infraspinatus.
Joints affected. Many muscles of the limb extend over two or more moveable joints
and the muscle will have an action on each of the joints that it crosses. However, the
extent of the muscle’s action on a particular joint will vary considerably owing to
physical considerations. The mass of the limb tapers from proximal to distal. The
distal limb, constitutes only a fraction of the mass of the limb at the shoulder and the
elbow. A muscle like the long head of the triceps brachii, which extends from the
scapula to the bones of the forearm, would have its chief effect on the more distal
elbow joint whether or not the proximal shoulder joint is held in position by the
contraction of other muscles. This is perhaps most easily seen in considering the
contraction of a muscle extending between a 2 kg weight and a 20 kg weight on a
frictionless surface. Contraction of the muscle will move the 2 kg weight ten times
farther than the distance moved by the 20 kg weight simply due to the difference in
mass to be moved. The digital flexor and extensor muscles that have their origin on
the humerus and extend to the digit will have their chief action on the digit and only
minimal action on the elbow and carpal joints, which they also cross.
The supraspinatus is the chief extensor of the shoulder joint, attaching distally to
the cranial prominence of the greater and lesser tubercles. From its lateral origin at
the supraspinatus fossa, its insertion on the medial lesser tubercle passes in front of
the scapula at the concavity of the scapular notch.
The infraspinatus acts chiefly to abduct the limb. The larger, more superficial, [(a)
in Fig. 1b] part of the muscle extends from the infraspinous fossa to the infraspinsatus
surface of the humerus. Where it passes over the caudal part of the lesser tubercle,
its large tendon is underlain by a prominent bursa. The smaller, deep, [(b) in Fig.1b]
part of the muscle arises from the infraspinous fossa at the neck. It inserts directly on
the caudal prominence of the greater tubercle.
The deltoideus is a flexor muscle of the shoulder joint. It arises with the
infraspinatus from the scapular spine and cartilage and lies superficial to the
infraspinatus. Distally it inserts on the deltoid tuberosity.
Teres minor is a small multipennate flexor muscle of the shoulder joint. It arises
from roughnesses of the distal infraspinous fossa and inserts on the teres minor
tuberosity just lateral to the line of triceps of the humerus. The tuberosity is well
defined in the dog but is hardly distinguished from the line of triceps in the Equidae.
Ellenberger-Baum, Springer Verlag: 1943; 237, shows a bursa underlying the muscle
where it passes over the caudal prominence of the greater tubercle.
The long head of the triceps brachii has its origin from the caudal margin of the
scapula distal to the facet for the teres major. This is a strong, multipennate, muscle
that inserts distally on the caudal part of the summit of the olecranon. With its lateral
and medial humeral heads, this muscle is the main extensor of the cubital joint. It
tends to flex the shoulder joint, but its chief action is extension of the more distal
cubital articulation. A subtendinous bursa is present cranially, between tendon and
olecranon.
The tensor fasciae antebrachii lies medial to the long head of triceps. It is a flat
muscle, arising in part from the caudal margin of the scapula, in part from the tendon
of the latissimus dorsi. Insertion is on the olecranon medial to the triceps tendon and
in part on the antebrachial fascia. A bursa is present deep to its olecranon insertion.
Its action is chiefly like that of the long head. This muscle is apparently split-off the
triceps; like the triceps, it is supplied by the radial nerve. This muscle is lacking in
humans.
The teres major passes from a facet at the caudodorsal angle of the scapula. It
passes distally on the medial side of the triceps and tensor fasciae antebrachii and
the latissimus dorsi. With the latissimus dorsi tendon, which joins the teres major
tendon laterally, it inserts on the teres major tuberosity on the medial side of the
humerus. The muscle is a strong flexor of the shoulder joint.
Subscapularis takes origin from the subscapular fossa and inserts on the caudal
prominence of the lesser tubercle. It is a strong adductor of the limb. A small bursa is
often present between its tendon and the lesser tubercle (Sisson; Saunders: 1914).
Coracobrachialis. From the coracoid process to the craniomedial surface of the
humeral shaft. Its tendon of origin crosses the subscapularis tendon medially and is
separated from it by a bursa. The fleshy part of the muscle passes medial to the teres
major and latissimus dorsi tendons at their insertion on the teres major tuberosity.
This muscle is certainly an adductor of the limb. Sisson accounts it also as a flexor of
the shoulder joint; Budras (Anatomy of the Horse; Schluetersche: 2009:88), states
that the muscle is an extensor of the shoulder joint. Owing to the muscle’s line of
force passing cranial to the joint’s horizontal axis of rotation, I think that the muscle
has to be an extensor.
Biceps brachii. From the supraglenoid tubercle to the radial tuberosity of the radius
and, by means of its lacertus fibrosus, the metacarpal tuberosity of MCIII. The tendon
of origin is substantial and fibrocartilaginous where it passes in the intertubercular
groove of the humerus. A deep sulcus of the tendon is adapted to the intertubercular
tubercle of the humerus and tends to hold the tendon in place. The tendon passes
without interruption and with some folding through the fleshy part of the muscle,
dividing distally into the more stout, medial, insertion at the radial tuberosity and the
more slight lateral branch, the lacertus fibrosus, which joins the tendon of the
extensor carpi radialis in the proximal forearm. A small bursa is between the tendon of
origin and the supraglenoid tubercle; a much larger bursa is present between the
tendon and the intertubercular groove, which is covered with a thin layer of cartilage.
A small bursa is deep to the muscle where it passes cranial to the cubital joint
capsule. This muscle, with the brachialis, is the chief flexor of the elbow joint. The
biceps tends to extend the shoulder joint; but its chief effect is on the elbow. The
tendons of the muscle form a prominent part of the stay apparatus of the equine
forelimb (discussed in a later presentation).
Note: the capsularis is a small, thin, muscle applied to the caudal aspect of the
humeral (shoulder) joint capsule. Its attachments are provided by the fibrous layer of
the joint capsule. Grossly, it appears to function to gather the joint capsule as the joint
is flexed. Similar capsular muscles (for example, the articularis genu of the dog) have
been shown to be composed of numerous neuromuscular spindles and have
therefore an obvious proprioceptive function. To the writer’s knowledge, this has not
been investigated in the Equidae.
Fig. 6a. L humerus of the
horse, lateral view. From
Sisson.
head
neck
body
(shaft,
diaphysis)
greater tubercle
condyle
Intertubercular
tubercle
intertubercular
groove
greater tubercle
lesser tubercle
facies infraspinati
deltoid
tuberosity
Intertubercular
tubercle
line of triceps
teres major
tuberosity
deltoid
tuberosity
humeral crest
brachial
groove
brachial
groove
Fig. 6c. L humerus,
cranial view. From
Sisson.
Fig. 6b. L humerus,
lateral view. From
Sisson.
Fig. 6d. L humerus,
medial view.
nutrient foramen
olecranon
olecranon
ulna
radial
tuberosity
radius
ulna
Fig. 7a. L radius
and ulna, medial
view. From Sisson.
Fig. 7b. L radius
and ulna, Lateral
view. From Sisson.
Muscles that extend from the humerus to the radius and ulna are brachialis, medial
and lateral heads of the triceps brachii, and the anconeus.
The brachialis arises in the brachial groove of the humerus and inserts on the
medial radius distal to the biceps. With the biceps brachii, it is a flexor of the elbow
joint.
The medial head of the triceps arises from the humeral shaft caudal to the teres
major tuberosity. It inserts on the summit of the olecranon medial to the attachment of
the long head. The lateral head of the triceps arises by a thin tendon from the line of
triceps and inserts on the summit of the olecranon lateral to the tendon of the long
head, which it joins. With the long head of the triceps, the lateral and medial heads
form the triceps brachii, the main extensor of the elbow joint.
The anconeus takes origin from the proximal margin of the olecranon fossa and
inserts on the lateral surface of the body of the olecranon. This muscle extends the
elbow joint.
Views showing areas of muscle attachment to the humerus, radius, and ulna:
Figures 8a – 8f are from O. Charnock Bradley, The
Topographical Anatomy of the Limbs of the Horse;
W. Green and Sons, Edinburgh: 1920.
Infraspinatus
(deep part)
supraspinatus
supraspinatus
Infraspinatus
(supf part)
teres minor
deltoideus
supraspinatus
triceps brachii,
subscapularis
lat head
brachialis
deep pectoral
teres major,
latissimus dorsi
deltoideus
ext carpi
radialis
coracobrachialis
brachiocephalicus, supf
pectoral (descending)
common digital
extensor
supf and deep digital
flexor muscles
ulnaris lateralis
ext. dig. communis
Fig. 8a. L humerus,
lateral view.
Fig. 8b. L humerus,
cranial view.
supraspinatus
Infraspinatus
(deep part)
(supf part)
teres minor
triceps,
lat head
subscapularis
capsularis
brachialis
deltoideus
triceps,
med head
anconeus
ulnaris
lateralis
flexor carpi
radialis
flexor carpi
ulnaris
supf, deep
digital flexors
supf, deep
digital flexors
flexor carpi
ulnaris
ulnaris
lateralis
subscapularis
Fig. 8d. L humerus, view
of proximal extremity.
Fig. 8e. L humerus, view
of distal extremity.
supraspinatus
deep pectoral
subscapularis
brachialis
teres major
latissimus dorsi
triceps brachii,
medial head
anconeus
coracobrachialis
Fig. 8f. L humerus,
medial view.
flexor carpi
radialis
supf, deep
Figures 9a – 9d are from O. Charnock Bradley,
The Topographical Anatomy of the Limbs of the
Horse; 1920, W. Green and Sons, Edinburgh.
triceps brachii,
long and lateral heads
tensor fasciae
antebrachii
anconeus
triceps brachii,
medial head
biceps
brachii
deep digital flexor,
ulnar head
Fig. 9a. Proximal L radius
and ulna, lateral view.
deep digital flexor,
ulnar head
biceps
brachii
biceps
brachii
brachialis
anconeus
Fig. 9b. Proximal L radius
and ulna, medial view.
triceps brachii,
long and lateral heads
triceps brachii,
medial head
tensor fasciae
antebrachii
deep digital flexor,
ulnar head
brachialis
Summary and discussion:
1. Extrinsic muscles of the forelimb attach the limb to the axial skeleton.
They act chiefly to draw the limb forward and backward in progression. The
extrinsic muscles that attach to the ribs and sternum also act in maximal
2.
3.
4.
5.
6.
7.
inspiration, drawing the ribs forward and outward to enlarge the transverse
diameter of the thorax and the sternum forward in enlarging the dorsoventral
diameter of the thorax. The fascial framework of the serratus ventralis
passively supports the trunk on the limbs. The serratus ventralis muscle
provides active support of the trunk on the limbs.
Cranial and caudal movement of the scapula determines the length of the
stride. The maximum forward movement of the scapula accompanied by
maximal exension of the limb sets the cranial limit of the stride and the
caudal limit is correspondingly determined. In these movements, contraction
of the cervical serratus ventralis is functional in forward movement, the
thoracic serratus ventralis in caudal movement.
Extrinsic muscles are: trapezius, rhomboideus, latissimus dorsi,
superficial and deep pectoral muscles, omohyoideus, serratus
ventralis, brachiocephalicus and omotransversarius.
Intrinsic muscles extend between the bones of the forelimb and are
responsible for movements of the forelimb joints. Extrinsic muscles also
have a limited effect on the shoulder joint of the forelimb.
Intrinsic muscles that act on the shoulder joint: supraspinatus,
coracobrachialis, infraspinatus, triceps brachii, subscapularis, ,
deltoideus, teres minor, tensor fasciae antebrachii, teres major, and the
biceps brachii. Main extensor: supraspinatus; it is assisted by the
coracobrachialis. Main flexors: teres major, teres minor, deltoideus; main
abductor: infraspinatus; main adductor: subscapularis. The capsularis acts
on the shoulder joint capsule. Its function in proprioception needs to be
evaluated. The long head of the triceps brachii and the tensor fasciae
antebrachii tend to flex the shoulder joint; the biceps brachii tends to extend
it. Their chief action, however, is on the more distal elbow joint.
Intrinsic muscles that act on the elbow joint: biceps brachii, brachialis,
triceps brachii, tensor fasciae antebrachii, and anconeus. The carpal
and digital extensor and flexor muscles that arise from the humerus also
have action on the elbow joint but their chief action is on the more distal
carpal and digital articulations. The biceps and brachialis are the main flexors
of the elbow joint; the triceps is the main extensor. The tensor fasciae
antebrachii and anconeus also act to extend the elbow joint.
Topography. Those muscles that lie just beneath the skin, including those
deep to the thin cutaneous muscle of the shoulder and arm (cutaneus
omobrachialis), are directly palpable and the bones and bony prominences
that attach these muscles are palpable: summits of the vertebral spinous
processes at the withers, ribs, ventral margin of the sternum and xiphoid
process and cartilage, tuber spinae of the scapula, deltoid tuberosity and
proximal humeral crest, and the olecranon. The greater tubercle is palpable
at the shoulder and the tendon of the superficial part of the infraspinatus is
easily palpated where it crosses over the caudal part of the greater tubercle.
The tendon of origin of the biceps is palpable where it is deep to the
brachiocephalicus. The jugular furrow is palpable and defines the apposed
borders of the brachiocephalicus dorsally and the sternocephalicus ventrally.
Caudally, where it passes over the external jugular vein, the thicker part of
the cutaneus colli is palpable.
The cutaneous muscles are shown in Fig. 10:
cutaneus
faciei
cutaneus
colli
cutaneus
omobrachialis
cutaneus
trunci
Fig. 10. Cutaneous
muscles.
The muscles immediately deep to the cutaneous muscles are shown in Fig. 11 (they
are labeled in Fig. 2, above):
Drawn by David
Stewart Geary
The belly of the biceps brachii is palpable where it lies immediately cranial to
the humerus, lateral to the humeral crest and brachial groove. The brachial groove is
occupied by the brachialis. The tendons of the brachiocephalicus (cleidobrachialis)
and descending superficial pectoral pass between the biceps and brachialis to attach
to the distal part of the deltoid tuberosity and to the humeral crest. Although the
biceps is deep to the brachiocephalicus, it is palpable as the biceps is a substantial
muscle and the brachiocephalicus is fairly thin. The brachialis, within the brachial
groove, is palpable but, owing to its relatively small exposure between the biceps
medially and the extensor carpi radialis laterally, is not clearly distinguished. Figs. 11,
12, and 13 show this relationship.
A.
B.
C.
Fig. 12. A, relationship of scapula, humerus, radius and ulna to
the thorax. B, major bone landmarks, C. relationship of biceps
prominence of greater
tubercle
omotransversarius
cleidobrachialis
descending supf
pectoral
transverse supf
pectoral
Brachialis lies beneath
deep fascia lateral to
humeral crest.
Fig. 13. Craniolateral view of left shoulder region,
cutaneuous muscles removed. The position of the deltoid
tuberosity and humeral crest to which the
cleidobrachialis and descending superficial pectoral
attach are shown by the dotted line. Drawn by David
Stewart Geary
Insertion of biceps and brachialis on the forearm (Fig. 14). The biceps is medial
to the brachialis on the arm. As the two muscles pass onto the medial forearm, they
are close together and no longer separated by the humeral crest. The biceps insertion
is the stronger as is indicated by the size of the radial tuberosity. Its antebrachial
insertion is chiefly on the large radial tuberosity; some of its tendon-fibers join the long
part of the medial collateral ligament of the elbow joint. The brachialis insertion is: 1)
By a long, slender tendon that lies in a distinct groove of the radius deep to the long
part of the medial collateral ligament of the elbow. The tendon is protected by a
synovial sheath where it lies between the bone and the ligament. The insertion of this
tendon is on the radius and ulna. 2) Its second insertion is by a band of fibers given
off to the long collateral ligament as the tendon begins to pass deep to that ligament.
These structures are palpable but not easily distinguished as they are deep to the
transverse part of the superficial pectoral muscle.
Fig. 14. Relations of biceps
and brachialis, diagrammatic.
supraspinatus
infraspinatus
Infraspinatus
superficial part
deep part
brachialis (cut)
biceps
brachialis (cut)
lacertus fibrosus
Fig. 15. Tendons of insertion of biceps and brachialis at the medial elbow.
Yellow, short collateral ligament; green, long collateral ligament; orange,
insertions of the biceps; blue, insertions of the brachialis. The position of the
synovial bursa of the brachialis is not shown; it encloses the brachialis tendon,
where it lies in the distinct groove of the proximal medial radius. Modified from
O. Charnock Bradley, The Topographical Anatomy of the Limbs of the Horse;
W. Green and Sons, Edinburgh: 1920,
humerus
ulna
short and long
medial collateral
ligaments of
elbow joint
biceps brachii
brachialis
radius
Short ligament
attaches here.
radial tuberosity
Brachialis tendon
attaches here.
groove for
brachialis tendon
Long ligament
attaches here.
This ends the presentation on movement of the shoulder and elbow joints. The
thoracic limb will also be covered on these subjects, but not necessarily in the order
listed:
3. movement of carpal and digital articulations;
4. joint topography and surface anatomy;
5. arteries and veins of the thoracic limb;
6. skin and cutaneous and subcutaneous structures;
7. surface anatomy of the shoulder, elbow, carpus, metacarpus and digits;
8. hoof.
Before continuing in this series on the forelimb, I am going to publish almost all of the
drawings that I have on the different species. It is taking me so long to do each part
that I am concerned that I won’t be able to get it all done if I try to elaborate on each
section. Anyone who wants to use this information is free to do so and can modify the
drawings that are not subject to copyright to suit his/her purpose. I have not had the
time to get it done. The computer programs used to publish the drawings are
powerpoint with the different toolbars available and Adobe’s Photoshop. I use a Mac,
which incorporates all of the Windows programs. The figures are generally free of
copyright but not all. I use Sisson’s 1914 edition and Bradley’s 1920 edition. Both are
available online. I modify the figures to fit the style used here, correct a few minor
mistakes---Sisson and Bradley were excellent anatomists and Ellenberger and Baum,
Grau, Ackernecht and Zietzschmann also---but otherwise have left them untouched.
The Ellenberger-Baum figures are still subject to copyright, at least as far as the 1943
edition is concerned. I have used these figures sparingly and, in all cases, Sisson,
Bradley, Ellenberger-Baum, Martin, have given them full credit and reference. Many
of the older figures were more accurate and more artistically pleasing than more
recent figures that appear. There are inaccuracies, of course, both old and new.
Those that I know, I correct.
With respect to those drawings published with my written permission and blessing by
Professor W.O. Sack, I retained the right to publish these drawings myself. Frankly, at
the time (1972) of my giving these drawings to Professor Sack to use as he saw fit, I
wasn’t thinking that I would be doing more in anatomy. I am interested in the subject
matter and didn’t want these things to be, so to speak, “lost.” We are indebted to
many fine anatomists, living and dead, for what we have of this useful science.
Aaron Horowitz, 29 June 2011