106 DISSECTION OF THE DOG 



Dissection. — Separate the remaining bones of the tarsus in order to 

 demonstrate the interosseous ligaments. 



Ligamenta tarsi interossea. — One of the interosseous ligaments — the talo- 

 calcanean — has already been studied. Others will now be found joining the 

 navicular to the cuboid, the cuboid to the lateral cuneiform, and the three 

 cuneiform bones. 



Articulationes intermetatarsem. — Weak dorsal and plantar ligaments unite 

 the bases of the metatarsal bones. The rigidity of the intermetatarsal joints 

 depends upon strong interosseous ligaments. 



Articulationes metatarso-phalangece. — The metatarsophalangeal joint is 

 formed by four bones ; namely, the metatarsal bone, the first phalanx, and two 

 sesamoid bones. The joint is enclosed by a capsule connected with the extensor 

 tendons in front. On each side of the joint is a collateral ligament which joins 

 the head of the metatarsal bone to the first phalanx and one of the sesamoid 

 bones. 



The sesamoid bones are firmly united to each other by a strong interosseous 

 ligament, and are further attached to the proximal part of the first phalanx 

 by ligaments on each side of the joint as well as on its plantar aspect. 



Articulationes digitorum pedis. — The joints between the first and second, 

 and second and third phalanges are provided with capsules and collateral 

 ligaments. In addition, the joint between the second and third phalanges 

 has two dorsal ligaments, which spring from the sides of the proximal end 

 of the second phalanx and are attached to the proximal end of the third 

 phalanx. 



Pelvis. — The pelvis is a cavity bounded by the sacrum and the two hip 

 bones, and differing in its contents dependent upon the sex. It is convenient 

 to suppose that the subject being dissected is a male. The contents of the 

 female pelvis will be considered later. 



The contents of the male pelvis may be tabulated as follows : — 



/ Rectum. 



I Possibly a small part of the prostate. 

 Viscera. -, Prostatic and membranous parts of 



the urethra. 

 Deferent ducts. 

 _ . . j Hypogastric vessels and their branches. 



( Middle sacral vessels. 



Nerves. J 



/ Pudendal nerve. 



j Sacral plexus and its branches. 



Obturator nerve. 



Sacral part of the sympathetic nervous 

 system. 



