180 OSTEOLOGY. 



than in those that are weak and debilitated. They are invested throughout their 

 whole surface by the fibrous tissue of the tendon in which they are found, excepting 

 upon that side which lies in contact with the part over which they play, where 

 they present a free articular facet. They may be divided into two kinds ; those 

 which glide over the articular surfaces of joints, and those which play over the 

 cartilaginous facets found on the surfaces of certain bones. 



The sesamoid bones of the joints are, in the lower extremity, the patella, which 

 is developed in the tendon of the Quadriceps extensor ; two small sesamoid bones, 

 found opposite the metatarso-phalangeal joint of the great toe in each foot, in the 

 tendons of the Flexor brevis pollicis, and occasionally one in the metatarso- 

 phalangeal joint of the second toe, the little toe, and, still more rarely, in the 

 third and fourth toes. 



In the upper extremity, there are two on the palmar surface of the metacarpo- 

 phalangeal joint in the thumb, developed in the tendons of the Flexor brevis 

 pollicis. Occasionally, one or two opposite the metacarpo-phalangeal articulations 

 of the fore and little fingers, and, still more rarely, one opposite the same joints 

 of the third and fourth fingers. 



Those found in tendons which glide over certain bones occupy the following 

 situations. One in the tendon of the Peroneus longus, where it glides through the 

 groove in the cuboid bone. One appears late in life in the tendon of the Tibialis 

 anticus, opposite the smooth facet on the internal cuneiform bone. One in the 

 tendon of the Tibialis posticus, opposite the inner side of the astragalus. One in 

 the outer head of the Gastrocnemius, behind the outer condyle of the femur; and 

 one in the Psoas and Iliacus, where they glide over the body of the pubes. 

 Occasionally in the tendon of the Biceps, opposite the tuberosity of the radius ; 

 in the tendon of the Gluteus maximus, as it passes over the great trochanter; 

 and in the tendons which wind round the inner and outer malleoli. 



The author has to acknowledge valuable aid derived from the perusal of the works of Cloquet, 

 Cruveilhier, Bourgery, and Boyer, especially of the latter. Reference has also been made to 

 the following: "Outlines of Human Osteology," by F. 0. Ward. "A Treatise on the Human 

 Skeleton, and Observations on the Limbs of Vertebrate Animals," by G. M. Humphry. Holden's 

 "Human Osteology." Henle's "Handbuch der Systematischen Anatomie des Menschen. Erster 

 Band. Erste Abtheilung. Knochenlehre." " Osteological Memoirs (The Clavicle)," by Stru- 

 thers. "On the Archetype and Homologies of the Vertebrate Skeleton," and "On the Nature 

 of Limbs," by Owen. Todd and Bowman's "Physiological Anatomy," and Kolliker's "Manual 

 of Human Microscopic Anatomy," contain the most complete account of the structure and 

 development of bone. The development of the bones is minutely described in "Quain's Ana- 

 tomy," edited by Sharpey and Ellis. On the chemical analysis of bone, refer to "Lehmann's 

 Physiological Chemistry," translated by Day, vol. iii. p. 12. "Simon's Chemistry," translated 

 by Day, vol. ii. p. 396. A paper by Dr. Stark, "On the Chemical Constitution of the Bones of 

 the Verteb rated Animals" (Edinburgh Medical and Surgical Journal, vol. liii. p. 308) ; and Dr. 

 Owen Bees's paper in the 21st vol. of the Medico-chirurgical Transactions. 



