Book One -- The things that sustain and support the entire body, and what braces and attaches them all. [the bones and the ligaments that interconnect them] | Chapter 24 On the Bones of the Forearm: the Ulna and Radius

What the ten figures that we have placed in order beneath the first figure of this chapter represent, and index of all the characters inscribed on the eleven figures.

In the second figure of the 24th chapter, both bones of the forearm, the radius and ulna, are shown in their outer [posterior] aspect. In the third, the radius alone is drawn on its inner [anterior] side; in the fourth, the radius on its outer [posterior] side. The fifth represents the inner [anterior] side of the ulna, the sixth the outer [posterior]. The seventh shows the lower [distal] portion of the right radius to which the carpus 2 is articulated. We have drawn this part as if from below, the side facing the ulna, so as to keep in view the depression [incisura ulnaris] where the tubercle or head of the ulna [caput ulnae] is received here next to the wrist. The eighth figure, like the three after it and the first six, belongs to the left 3 forearm; it shows the lower part of the radius in its exterior aspect [facies posterior], so drawn as to reveal the depression [facies articularis carpalis] into which the carpus is articulated. The ninth illustrates the upper part [caput radii] of the radius, in which is seen the socket [fovea articularis] which the outer head of the humerus [capitulum humeri] enters. The tenth represents the lower portion of the ulna [caput ulnae], illustrating the part [circumferentia articularis] that faces the carpus. The eleventh shows the upper part of the ulna where the depressions, protuberances, and processes occur in which the groove or trochlea of the humerus is fitted.

A, B 1 , 2 The interval enclosed by these letters is called the cubitus or forearm [antebrachium]; A marks its superior [proximal] part, which is attached to the humerus, B the inferior [distal], which faces the carpus. If you desire any names of this area and its bones, you can look them up easily at the end of this Book. 4
C 1 , 5 , 11 Anterior process [p. coronoideus] of the ulna, entering the depression [fossa coronoidea] of the humerus carved in the anterior part of the upper surface of the trochlea. In the first figure, C marks the inner surface of the process, which is covered with cartilage; in the fifth and eleventh, it indicates the rough, uneven outer surface.
D 1 , 2, 5 , 11 Posterior process [olecranon] of the ulna which enters the depression cut in the posterior surface of the humerus [fossa olecrani] next to the upper region of the trochlea. In the first, second, and fifth figure, D marks the inner surface of the process; in the eleventh it marks the outer or posterior.
E 1 , 2, 5 Depression [incisura trochlearis] of the ulna that receives the trochlea of the humerus. The eleventh figure marks this depression more exactly.
F, F[ 11 ] 5 These mark the swelling that runs along the longitude of this depression.
G, G[ 11 ] The inner side of the swelling.
H, H[ 11 ] Outer side of the swelling or, if you prefer, of the depression of the ulna.
I, K[ 11 ] Area of this depression where it is interrupted a little at its sides in the lowest part so that it is not a smooth circumference, and is somewhat rough and a little porous so as to put forth ligaments.
L 1 , 5 , 11 Small processes [tuberositas ulnae] and a great roughness in the root of the anterior process of the ulna marked C, providing a suitable area for the origin and insertion of certain muscles. 6
M 1 , 2, 3, 4 , 9 Cervix or neck of the radius [collum radii] .
N 1 , 2, 3, 4 , 9 Capitulum of the radius [caput radii] in which a depression [fovea articularis] is carved that receives the outer head of the humerus;
O[ 9 ] this depression [fovea articularis] is marked O in the ninth figure.
P 1 , 2, 5, 6 , 10 Neck of the ulna.
Q[ 1 , 2, 5, 6 , 10 ] In the same figures, the epiphysis of the ulna is marked Q.
R 1 , 2, 5, 6 , 10 Process [p. styloideus] of the epiphysis of the ulna, which we compare to a writer’s stylus.
S 10 Depression 7 of the epiphysis of the ulna to which is attached or rather inserted a certain cartilage to be marked T, originating from the depression of the radius, where it holds the carpus.
T 1 , 2, 3, 4 , 7, 8 Cartilage [discus articularis] just mentioned which separates the largest portion of the epiphysis of the ulna from the carpus; in the first and eighth figure it marks the area of cartilage where it first originates


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from the depression in the epiphysis of the radius that will be marked x, y, z. In the second figure it marks the part where the cartilage attaches to the epiphysis of the radius. 8 In the third, it marks the area of cartilage facing the carpus; in the fourth, 9 the area of the cartilage that rests upon the ulna.
V 2, 6 , 10 Depression in the epiphysis of the ulna and the bone of the ulna 10 to which the epiphysis is attached, provided here to bring down the tendon of one of the muscles that extend the carpus.
X, Y, Z[ 2, 6 ] These three characters in the the sixth figure, and X and Z in the second, describe a triangle 11 in the ulna which is unfleshed 12 and convex. Z by itself marks the vertex of the triangle.
a, a 1 , 2, 6 First protruding line [margo posterior] of the ulna.
b, b 1 , 5 Second protruding line [margo anterior] of the ulna. b by itself in the first and fifth figures shows the portion of this line that runs obliquely along the neck of the ulna.
c, c 1 , 2, 5 Third protruding line [margo interosseus] of the ulna.
d 1 , 6 Side [facies medialis] of the ulna circumscribed by the first and second line.
e 2, 6 Side [facies posterior] of the ulna circumscribed by the first and third line.
f 1 , 5 Side [facies anterior] of the ulna between the second and third line.
g, g 2, 6 Line peculiar to the side which is enclosed by the first and third line.
h, i 1 These two characters mark the points where the radius is attached to the ulna; h identifies the superior point [articulatio radio-ulnaris proximalis], i the lower point [articulatio radio-ulnaris distalis], adjacent to the carpus.
k, k 1 Throughout this area (because the radius is curved like a bow), the two bones of the forearm stand apart from each other.
l 5 , 11 Depression [incisura radialis] carved in the ulna, in which the head of the radius turns.
m 3, 4 , 9 Area of the head of the radius [circumferentia articularis] which fits in the depression of the ulna marked l.
n 1 , 3 Inner surface of the lower epiphysis of the radius; in the remaining figures, i.e., the second, fourth, seventh, and eighth, the outer surface is shown with other characters.
o 7 Depression [incisura ulnaris] carved in the epiphysis of the radius, in which the epiphysis of the ulna is received.
p 5 , 10 Protruding part of the epiphysis of the ulna [caput ulnae, circumferentia articularis] that enters the depression of the radius marked o.
q 1 , 2, 3, 4 , 9 Large, blunt process of the [radius tuberositas radii], 13 into which the tendon of the anterior of the muscles [m. biceps brachii] that flex the forearm is inserted.
r, r 1 , 2, 3, 4 Sharp line [margo interosseus] on the lower surface of the radius, protruding where it faces the ulna along the longitude of the forearm.
s, s 1 , 3 Inner side [facies anterior] of the line previously marked r.
t, t 2, 4 Outer side [facies posterior] of the line marked r.
u 2, 4 14 At this point [facies lateralis] the radius is rough, so that two of the four muscles [m. pronator teres] [m. supinator] peculiar to it may be be more firmly inserted here.
x, y, z 1 , 8 Depression [facies articularis carpalis] cut in the epiphysis of the radius for articulation with the carpus; z notes the tubercle of the depression protruding somewhat, making it a kind of double depression whose parts can be identified as x and y. 15
a 1 , 3, 4 , 7, 8 The most prominent portion [proc. styloideum] of the epiphysis of the radius, augmenting the depression to which the carpus is articulated 16 on its upper or inner surface and protruding higher than the process of the epiphysis of the ulna that resembles a stylus and is marked R.
g, d, e, z, h [ 2, 4 ] By these characters in the second and fourth figures, the convex outer region of the lower epiphysis of the radius is identified, together with the area of the bone to which the epiphysis is fused. Each character marks a separate depression in this area; g identifies the first depression, d the second, e and z the third, h the fourth. 17
q [ 2 ] In the second figure, q identifies the depression [incisura ulnaris] common to the radius and the ulna. 18



Book One -- The things that sustain and support the entire body, and what braces and attaches them all. [the bones and the ligaments that interconnect them] | Chapter 24 On the Bones of the Forearm: the Ulna and Radius