34 MAMMALIAN ANATOMY 



or fovea, and a faint depression, by some writers, is called an im- 

 pression, impressio. 



A groove (sulcus) is a narrow furrow on a bone. Example : 

 bicipital groove on the humerus, sulcus bicipitalis. 



A deep cut in the border of a bone is termed a notch (incisura). 

 Example : coracoid notch of the scapula, incisura coracoidea. 



(3) The exterior of a bone exhibits openings leading into the 

 substance of the bone or into cavities of the interior. 



The general term for an opening in a bone is fora'men (a door). 

 It is used in several ways : for example, 



1. A foramen may be an aperture leading into a narrow passage 

 extending through one or more bones. Examples : stylomastoid 

 foramen, foramen stylomastoideum of the temporal bone, leading into 

 the facial canal ; the nutrient foramina, foramina nutritia, of all bones. 



2. A foramen may be a large opening through one thin bone 

 or between several bones. Examples : foramen magnum of the occip- 

 ital bone ; obturator foramen of the innominate, foramen obturatum. 



The membranous spaces between some of the skull bones at birth 

 are termed fontanelles or fontanels (fonticuli). 



3. The meaning of the term foramen may be extended to include 

 a short passage-way itself. Example : optic foramen in the sphenoid, 

 foramen opticum, which is strictly a passage opening by two foramina. 



The term aperture is also used for an opening. Example : the 

 nasal aperture, apertura nasal is. 



A fissure is a slit or an elongated opening, usually between two or 

 more bones. Example : sphenoidal fissure, jissura sphenoidalis. 



The term hiatus (from hiare, to gape) is used a few times only, 

 to designate an opening into a cavity or a canal. Example : h latus 

 Fallopii in the temporal bone. It has also been used in place of the 

 term notch. 



CAVITIES AND PASSAGES IN BONES. 



Cavity (racitas, cavum} is applied to a space in the interior of one 

 bone. Examples : medullary cavity or cavum medullare, tympanic 

 cavity or tympanum. It is also applied to a space enclosed by several 

 bones. Examples : cavity of the mouth, cavum oris ; thoracic cavity, 

 cavum thoracis. A cavity containing air and having a narrowed outlet, 

 is called a sinus (a hollow). Example: frontal sinus, s'unix frontalis. 



