THE ARTICULATIONS IN BIHDS. 22ft 



the passage of the poiiorans tendons. It is confounded, on its sides, with tlie 

 culcaneo-metatarsal, and the internal and supei-ficial tibio-tai-sal hgaments. 



5. An interosseous ligament, attached to the four bones composing this 

 articulation. 



It is provided with a particular synovial membrane which always communi- 

 cates, in front, with the tibio-tarsul capsule. This membrane is prolonged, 

 superiorly, between the calcis and astragah;s, to lubrify two of the facets by 

 \vl)ich these bones come into contact ; and, in addition, it descends between the 

 cuboid and scaphoid bones, to form a third prolongation for the anterior cuboido- 

 scaphoid arthrodia. 



Movements almost null. 



Takso-metatarsal Articulation. — This joint, formed by the meeting of 

 the three tarsal bones — the cuboid and the two cuneiforms— with the three bones 

 of the metatarsus, is fixed by the lateral superficial ligaments of the tibio-tarsal 

 articulation, the calcaneo-metatarsal hgament, those which have been named the 

 astragalo-metatarsal and tarso-metatarsal, and by a strong interosseous ligament 

 which naturally forms tliree fasciculi. 



The synovial membrane proper to this joint ascends into the small anterior 

 cuboido-cunean arthrodia, and into that which unites the two cuneiform bones ; it 

 descends to the intermetatarsal articulations. 



Movements nearly luiU. 



In all tlie domesticated animals except Solipeds, the tarsal articulations offer some differen- 

 tial peculiarities, the study of which is without interest, as it is without utility. It is only 

 necessary to remark that the immobility of the tarsal joints, properly so called, is less absolute 

 than in Solipeds, owing to the peculiar configuration of the articular surfaces of some of the 

 bones composing them. Thus, in the Ox, Sheep, Goat, and Pig, the calcis is joined to the 

 astra;>:ahi8 by a real trochlear articulation, and the latter bone is united to the scaphoid by a 

 diarthrodial joint of the same kind — a mode of articulation much more favourable to motion 

 than that of the plauiforin diarthrodial joint. In the Dog and Cat, the same result is 

 obtained by the reception of the head of tlie astragalus into the superior cavity of tlte scaphoid. 



In Ruminants and the Pig, it is also observed that the til)io-tar.sal articulation is formed 

 by tlie tibia and fibula in the one direction, and by the astragalus and os calcis in the other. 



Lemoiu'ne, who has been again recently studying the mechanical arrangement of the Ox's 

 hock, remarks that, if tlie mobility of all the tarsal articulations deprive the po.sterior limb of 

 that anim il of the rigidity necessary for speed, yet the nature of the astragalo-calcanean articu- 

 lation givt s it great power. In fact, the posterior trochlea of the astragalus acts as an eccentric 

 on the calcis during movement, and gradually separates this bone in such a manner that the 

 tendon of the gastrocnemius always remains nearly perpendicular on the lever arm — no matter 

 to what degree the hock may be open or closed. But this mechanism may perhaps be disputed. 



CHAPTER III. 

 THE ARTICULATIONS IN BIRDS. 



The study of the articulations in birds will only arrest us for a few moments ; as 

 it will be confined to some remarks on the intervertebral occipito-atloid and 

 temporo-maxillary joints, the only ones exliibiting a special conformation worthy 

 of attention. 



Intervertet/ral articulations. — The great mobility of the neck of Birds is not 

 only due to the fact of its length, relatively considered, but also to the peculiar 

 manner in wliich the vertebrae of this portion of the spine are articulated. It will 



