GLOSSARY 449 



Omentum. Any fold of peritoneum attaching an organ to the 

 stomach. The greater omentum overlies the small intestines like 

 an apron. 



Opponens. (From the Latin words ob, "against;" ponere, "to 

 place.") Opposing. 



Opponens Minimi Digiti (muscle). The muscle which places the 

 little finger opposite to the thumb. 



Opponens Pollicis (muscle). The muscle which places the thumb 

 opposite to the little finger. 



Optic Chiasm. (See Chiasm.) 



Orbicularis Oris (muscle). From the Latin word orbiculus, a dim. 

 of orbis, "a circle.") The circular one of the mouth. 



Orbicularis Palpebrarum (muscle). The circular one of the eyelids. 



Orbit. (From the Latin word orbita, from orbis, "a circle.") The 

 bony pyramidal cavity containing the eye and its muscles, etc. 



Orbital. Pertaining to the orbit. 



Organic. (From the Greek word meaning an organ.) Having or 

 pertaining to, or characterized by organs; relating to the animal and 

 vegetable worlds; affecting the structure of organs. 



Orifice. (From the Latin words orificium; os, "a mouth;" facere, 

 "to make.") An opening or outlet of hollow organs, or between 

 organs. 



Os Innominata (bone) (pi. ossa innominatse) . (From the Latin 

 os, "a bone;" innominata, in, "without;" nomen, "a name.") The 

 nameless bone, due to its not resembling any known object. 



Os Magnum. (The great bone.) The third bone of the second 

 row of carpal bones (bones of the wrist). 



Osmosis. (The passage of liquids and substances in solution through 

 porous septa (a partition) . 



Osseocartilaginous. Formed of, or pertaining to bone and cartilage 

 as one. 



Ossicle. (From the Latin word ossiculum, a dim. of os, "a bone.") 

 A small bone. Auditory ossicles or chain of small bones found in the 

 middle ear. They are the incus, stapes, and malleus. 



Ossification. From the Latin words os, "a bone;" facere, "to make.") 

 The process of bone formation. 



Osteoblasts. Cells concerned in the formation of bony tissue 



steoclasts. The multinuclear (many nuclei) cells found against 

 the surface of bone in little eroded depressions (Howship's fovea), 

 and concerned in the removal of bone. 



Ostium Uterinum or Uteri. The mouth of the uterus (womb) . 



Ovum. (From the Latin word ovum, "an egg.") The reproductive 

 cell of an animal or vegetable, an egg. 



Oxidation. (From the Greek word meaning sharp.) The act or 

 process of combining with oxygen, as the hemoglobin of the red cells 

 does during respiration, and the cells of the tissues combine with it 

 as the hemoglobin of the red cells in the blood gives it up upon reaching 

 them. Oxidation is essential to body metabolism. 



Oxygen. Is a colorless, tasteless, odorless gas, one of the non- 

 metallic elements. It constitutes one-fifth of the atmosphere, eight- 

 ninths of water, three-fourths of organized bodies, and about one-half 

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