Po'rus op'ticus (L. optic pore). The place where the optic nerve 



enters the eye, and which is usually termed the " blind 



spot." 

 Post'axial. A term applied to that surface of a limb which, 



when the limb is at right angles to the spinal column, is 



posterior (towards the tail). 

 Postclavi'cula (L. post, after; davfada, the collar-bone). A 



bone sometimes formed in connexion with the pectoral 



arch in the Teleostean fishes. 

 Poste'rior (L. following after). Towards the tail ; behind. In 



Human Anatomy sometimes used in the sense of dorsal. 

 Post-fron'tal (L. post, after). A bone occurring in some Ver- 



tebrata behind the orbit above the alisphenoid. 

 Postfur'ca (L. post, after ; furca, a fork). Processes projecting 



from the sternal wall of each thoracic somite into the 



thorax in some Insecta. 

 Posto'ral (L. post, after; os, cris, the mouth). Behind the 



mouth. 

 Postsphe'noid (L. post, after). A separate ossification of the 



posterior part of the sphenoid bone of the skull, seen in 



infancy. 

 Prseco'racoid (L. prcz, before; coracoid tone). A bone found 



in some Vertebrata on the ventral surface of the pectoral 



arch. 

 Praemo'lar (L.pra, before; molar tooth}. The name applied 



to those double teeth which are situated anteriorly to the 



molar teeth. It is usual in Anatomy to apply the term to 



those permanent grinders which replace the milk molars 



of the first or temporary dentition. 

 Prsena'sal car'tilages. The anterior processes of the chondro- 



cranium of the frog. 

 Praeo'ral (L. pr<z, before ; os, oris, the mouth). In front of 



the mouth. 



Praesto'mium (L. prce, before ; Gr. stoma, a mouth). A seg- 

 ment of the body which precedes the mouth. 

 Preaxial. Applied to that surface of a limb which, when the 



limb is at right angles to the spinal column, is anterior 



(towards the head). 

 Predicro'tic (L. prce, before; Gr. dikrotos, striking on both 



sides). Applied to the secondary pulse wave which pre- 

 cedes the dlcrotic secondary wave. 

 Prefron'tal (L. prce, before ; frontal bone). A bone developed 



in some Vertebrata anteriorly to the frontal bone of the skull. 



