376 GLOSSARY 



De-cus-sa'tion of the pyramids ( Lat. decussatio, crossing) . the cross- 

 ing of the bundles of white nerve fibers called the pyramids, in the 

 medulla oblongata. 



De-lir'i-um tre'mens (Lat. delirium, madness, and tremens, trembling) : 

 a disorder of the brain due to the excessive use of ardent spirits. 



Den'tine (Lat. dens, dentis, tooth): the principal solid tissue of the 

 teeth. 



Der'mis (Gr. derma, the skin) : the corium, or true skin. 



Di'a-phragm ((Jr. diaphragma, a partition wall) : the membranous and 

 muscular division between the thorax and the abdomen. 



Dif-fer-en-ti-a'tion of tissues (Lat. differentia, difference) : that modi- 

 fication in the structure of the tissues which adapts them to dif- 

 ferent functions. 



Dif-fu'sion of gases : the homogeneous mixture which takes place in 

 two gases placed in contact. 



Di-ges'tion (Lat. digestio) : conversion of food in the alimentary canal 

 into products which can be absorbed into the blood. 



Dor'sal (Lat. dorsum, the back) : of or pertaining to the back, as 

 dorsal m uscles ; opposed to ventral. 



Duct: a tube or canal; especially one conveying secretion from a 

 gland. 



Du-o-de'num (Lat. duodeni, twelve each: because the length of the 

 duodenum is about twelve fingers' breadth) : the first division of 

 the small intestine, next the stomach. 



Du'ra ma'ter (Lat., hard mother. The membrane was once thought 

 to give rise to every membrane of the body) : the tough, fibrous 

 membrane surrounding the brain and spinal cord and lining the 

 cavities of the skull and spinal column. 



Em'bry-0 (Gr. embruori) : the early form of an animal in develop- 

 ment. 



E-mul'sion (Lat. emulgere, emulsum, to milk out) : a mixture of 

 liquids which do not dissolve, the particles of one floating as small 

 globules in the other; as fat (butter) in milk. 



En-am'el: the hard outer part of the tooth. 



End bulbs : one form of touch end organs. 



End organs : special nerve cells or groups of nerve cells which receive 

 and pass on the stimulus to which they are adapted. 



End plate : the branching termination of a nerve fiber in a muscle 

 cell. 



