282 OSTEOLOGY. 



Fibula. The fibula may be ridged and grooved in a remarkable manner, as is the case in 

 many bones of prehistoric races. This is probably associated with a greater development and 

 perhaps with more active nse of the muscles attached to it. 



The proximal articular facet varies much in size. Bennett (Dublin Journ. Med. Sc., Aug. 

 1891) records a case in which it was double, and also notes the occurrence of specimens in which 

 it was absent and in which the head of the bone did not reach the lateral condyle of the tibia. 



Many instances of partial or complete absence of the bone have been published. (Lefebre, 

 Contribution a I'e'tude de I'absence congSnitale du perqng, Lille, 1895.) 



Talus. The anterior calcanean facet is sometimes separated from the middle by a non- 

 articular furrow. The posterior process, often largely developed, is occasionally (2*6 per cent.) 

 a separate ossicle forming what is known as the os trigonum (Bardeleben) ; or it may be 

 united to the body of the talus by a distinct synchondrosis. A smooth articular surface may 

 occasionally be found on the medial side of the proximal surface of the neck. This is a pressure 

 facet dependent on -the frequent use of the ankle-joint in a condition of extreme flexion, and 

 is caused by the opposition of the bone against the anterior edge of the distal end of the tibia. 



The form of the bone at birth differs from that of the adult in that the medial splay of the 

 neck on the body is more pronounced, forming on an average an angle of 35 as compared with 

 a mean of 12 in the adult ; moreover, the articular surface for the medial malleolus extends 

 forwards along the medial side of the neck, and to some extent overruns its superior surface. 

 This is doubtless a consequence of the inverted position of the foot maintained by the foetus 

 during intra-uterine life. In these respects the fo3tal bone conforms to the anthropoid type. 



For a detailed study of the varieties of this bone, see K. B. S. Sewell. (Journ. Anat. and Physiol. 

 voL xxxviii.) 



Calcaneus. The trochlear process is occasionally unduly prominent, constituting the sub- 

 malleolar apophysis of Hyrtl, and cases are recorded of the calcaneus articulating with the 

 navicular. (Morestin, H., Bull de la Soc. Anat. de Paris, 1894, 5 e se"r. t 8, n. 24, p. 798 ; and 

 Petrini, Atti del XL Gongr. Med. Internaz. Roma, 1894, vol. ii., "Anat." p. 71.) Pfitzner (Morpho- 

 logische Arbeiten, vol. vi. p. 245) also records the separation of the sustentaculum tali to form 

 os sustentaculi. (See also P. P. Laidlaw, Journ. Anat. and Physiol. vol. xxxviii. p. 133.) 



Navicular. According to Manners Smith this bone displays more variety of form the 

 any other of the tarsal bones. He accounts for this both on morphological and mechanic 

 grounds. He regards the tuberosity as probably of threefold origin, an apophysial, an epiphysir 

 and a sesamoid element, the latter being the so-called sesamoid bone in the tendon of the 

 tibialis posterior. Cases are recorded where the tuberosity has formed an independent ossicle. 



Cuneiform Bones. Numerous cases of division of the first cuneiform bone into doi 

 and plantar parts have been recorded ; the frequent division of its metatarsal articular facet is 

 doubt correlated with this anomalous condition. T. Dwight has described (Anat. Anz. vol. xx. 

 p. 465) in two instances the occurrence of an os intercunetforme. The ossicle so named lies on 

 the dorsum of the foot at the posterior end of the line of articulation between the first and 

 second cuneiform bones. 



Cuboid. Blandin has recorded a case of division of the cuboid. Occasionally there is a 

 facet on the lateral surface of the bone for articulation with the tuberosity of the fifth metatarsal 

 (Manners Smith). 



Tarsus as a Whole. Increase in the number of the tarsal elements may be due to the 

 occurrence of division of either the first cuneiform or the cuboid bone, or to the occasional 

 presence of an os trigonum. Cases of separation of the tuberosity of the navicular bone have 

 been recorded, and instances of supernumerary ossicles between the first cuneiform and 

 second metatarsal bone have been noted. Stieda mentions the occurrence of a small ossicle 

 in connexion with the articular surface on the anterior and upper part of the calcaneus, and 

 Pfitzner notes the occurrence of an os sustentaculi. For further information on the variations 

 of the skeleton of the foot, see Pfitzner. (Morphologische Arbeiten, vol. vi. p. 245.) 



The possibility of an injury having been the cause of the occurrence of some of these so-called 

 supernumerary ossicles must not be overlooked. The use of the Rontgen rays has proved that 

 accidents of this kind are much more frequent than was at first supposed. 



The reduction in the number of the tarsus is due to the osseous union of adjacent bones. In 

 many instances this is undoubtedly pathological, but cases have been noticed (Leboucq) of fusion 

 of the cartilaginous elements of the calcaneus and talus, and the calcaneus and navicular 

 in foetuses of the third month. 



Metatarsal Bones. Several instances of separation of the tuberosity of the fifth metatarsal 

 (os Vesaleanum) have been recorded, whilst numerous examples of an os intermetatarsum between 

 the bases of the first and second metatarsal bones have been recorded by Gruber and others. 

 The tubercle on the base of the first metatarsal for the attachment of the peronaeus longus tendon 

 is occasionally met with as a separate ossicle. An epiphysis over the spot where the tuberosity 

 of the fifth metatarsal rests on the ground has been described. (Kirchner, Archiv klin. Chir. B 80.) 



Phalanges. It is not uncommon to meet with fusion of the second and third phalanges, 

 particularly in the fifth, less frequently in the fourth, and occasionally in the second and third 

 toes. The union of the phalangeal elements has been observed in the foetus as well as the 

 adult (Pfitzner). The proportionate length of the phalanges varies much ; in some cases the 

 ungual phalanges are of fair size, the bones of the second row being mere nodules, whilst in other 

 instances the reduction in size of the terminal phalanges is most marked. 



