EXTERNAL FEATURES. 17 
“I 
(c) The anal aperture (anus), and on either side of it the 
inguinal spaces, hairless depressions, on which the ducts 
of the inguinal glands open. 
(d) In the male: the urinogenital aperture at the extremity of 
the penis; the latter enclosed by a fold of integument, the 
prepuce (praeputium); the scrotal sacs (scrotum), lateral 
sacs of the integument lodging the testes. 
(e) In the female: the urinogenital aperture, enclosed by folds 
of the integument, forming the vulva. The clitoris, the 
homologue of the penis, is contained in its ventral wall. The 
mammary nipples (papillae mammarum), eight (to ten) in 
number on the ventral surface of the breast and abdomen. 
(f) The following skeletal points: on the axial skeleton, the 
manubrium sterni, xiphoid process, costal arch, spinous 
processes of thoracic and lumbar vertebrae; on the pectoral 
girdle, the acromion, clavicle, and respective borders and 
angles of the scapula; on the pelvic girdle, the iliac crest, 
pubic symphysis, and ischial tuberosity. 
4. In the anterior limb: 
(a) The division of the free portion into three segments, the 
arm (brachium), forearm (antibrachium), and hand 
(manus). 
(b) The position of the elbow (cubitus) in comparison with the 
knee. 
(c) The five digits, designated from the medial side as: first 
(d. primus), or pollex, second (d. secundus), or index, 
third or middle (d. tertius s. medius), fourth (d. quartus), 
and fifth (d. quintus s. minimus). 
5. In the posterior limb: 
(a) The division into three segments, the thigh (femur), leg 
(crus), and foot (pes). 
(b) The knee (genu), and the popliteal fossa of its posterior 
surface, the latter not well defined. The projection of the 
heel (calx), and the angle formed by the foot with the leg. 
(c) The four digits (dd. secundus-quintus). The vestigial first 
digit, or hallux, is not distinguishable externally. 
