ARTICULATION. 35 



IV. 



ARTICULATION, 



AN articulation is a union of any two sclerous segments 

 of an organism through the intervention of a substance dif- 

 fering from both. 



Synarthrosis (stiff joints). 



Sutura example, between bones of vertebrate skull, and 

 exo-skeleton of Dasypus (Armadillo). 



Gomphosis example, insertion of alveolar teeth. 



Schindjlesis example, rostrum of sphenoid with vomer. 



Amphiarthrosis (joints mixed) example, Isis, Gorgonia, Pen- 

 tacrinus, articulation of bodies of vertebrae in Mammalia. 



Diarthrosis (synovial joints). 



Arthrodia (sliding joint) example, symphysis pubis of 

 human pelvis. 



Enarthrosis (ball-and-socket joint) example, vertebrae of 

 Ophidia; occipito-atloid, articulation of jC^fostews(garpike); 

 spines of Echinodermata. 



Ginglimus (hinge joint) example, articulates generally. 

 Here the movement between member of a limb is lateral, 

 excepting Acoetes lupina, where it is vertical: hinge joint of 

 bivalve shells, tempora-maxillary joint of mammalia. 



Peculiar apparatuses. Spiral valve of Brachiopoda, pediculi 

 and ambulatory apparatus of Toxopneustes (sea urchin); pec- 

 toral fin of Pim.elodas (catfish); structure of joints in extremi- 

 ties of birds; hock joint of horse; hip joint of Phoca (seal); 

 and tibio-astragaloid articulation of certain Dinosaurian 

 reptiles. 



