o. 



Obli'quus abdo'minis exter'nus (L. external oblique of the ab- 

 domen). One of the muscles of the abdomen. 



Obli'quus abdo'minis inter'nus (L. internal oblique of the ab- 

 domen) . One of the muscles of the abdomen. 



Obli'quus ca'pitis infe'rior (L. lower oblique of the head). One 

 of the posterior cranio-vertebral muscles. 



Obli'quus ca'pitis supe'rior (L. upper oblique of the head). 

 One of the posterior cranio-vertebral muscles. 



Obturato'rius (L. obturo, I stop up). Two muscles of the 

 dorsal surface of the thigh (internal and external). 



Occi'pital (L. occiput, the back of the head). Relating to the 

 back of the head, as the occipital bone. 



Occi'pital fora'men (L. occiput, the back of the head ; foramen, 

 an opening, window). The opening by which, in the 

 Insecta, the cavity of the head communicates with that of 

 the neck. 



Occipita'lis muscle (L. occiput, the back of the head). A 

 muscle of the back of the head. 



OccT'pito-fronta'les muscles. Muscles in the hedgehog which 

 are attached to the occipital crest, and are inserted into 

 the integument over the frontal and nasal bones. 



Occi'pito-mas'toid su'ture (L. occiput, the back of the head ; 

 mastoid bone ; sutura, a seam). A continuation of the 

 lambdoidal suture of the skull. 



Occi'pito-pari'etal su'ture (L. occiptit, the back of the head ; 

 parietal bone ; suttira, a seam). The suture which con- 

 nects the occipital and parietal bones of the skull. 



Occi'pito-pari'etal sul'cus. The depression between the oc- 

 cipital and parietal lobes of the cerebrum. 



Ocelli (L. little eyes). The simple eyes of the Invertebrata. 



Octo'merus (Gr. okto, eight; meros, a part). Consisting of 

 eight parts. 



Octo'poda (Gr. okto, eight ; pous, podos, a foot). A group of 

 the Cephalopoda, the members of which have eight arms. 



O'cular ten'tacle (L. oculus, eye). The tentacle which in some 

 Mollusca bears the eye. 



O'culo-mo'tor nerve (L. oculus, eye ; motor, mover). The third 

 cerebral nerve supplied to four out of the six eye muscles. 



Odon'toblasts (Gr. odous, odontos, a tooth; blastos, a germ). 

 Oblong cells in the pulp of a tooth. 



