THE ARTICULATIONS IN BIRDS. 22S 



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

 calcaneo-metatarsal, and the internal and superficial tibio-tarsal ligaments. 



5. An interosseous liyamenf, 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-tarsal capsule. This membrane is prolonged, 

 superiorly, between the calcis and astragalus, to lubrify two of the facets by 

 which 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-metataesal Aeticulation. — 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 three 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 null. 



In all the 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 

 astragalus 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 planiform 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 the scaphoid. 



In Ruminants and the Pig, it is also observed that the tibio-tarsal articulation is formed 

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



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

 hock, remarks that, if the mobility of all the tarsal articulations deprive the posterior limb of 

 that animal of the rigidity necessary fur speed, yet the nature of the astragalo-calcanean articu- 

 lation gives 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 exhibiting a special conformation worthy 

 of attention. 



Intervertebral articulations. — The great mobility of the neck of Birds is not 

 only due to the fact of its length, relati^'ely considered, but also to the peculiar 

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



