FOOTPRINTS IN THE SANDS OF TIME. 249 



such as trails, footprints, burrows, and coprolitic or other 

 organic material found in the rocks. Pythagoras, Plato, 

 Aristotle, and other ancients, allude to the existence of ma- 

 rine shells at a distance from the sea : it was considered con- 

 clusive evidence that the rocks containing them had formerly 

 been submerged beneath the ocean. Am. Cyc. 



PAPII/LA. The end of the nipple, or an eminence ^imilar to a 

 nipple. 



The minute elevations of the surface of the skin, tongue, 

 &c. They serve to increase the extent of surface for vascular 

 distribution, or subserve sensitive or mechanical purposes. 

 Some contain one or more vascular loops ; others, nervous 

 elements. Some are surmounted by dense epithelial fila- 

 ments, as those which give the roughness to the tongue. 



Webster. 



PAR'ASITE. Parasites are plants which attach themselves to 

 other plants, and animals which live in or on the bodies of 

 other animals, so as to subsist at their expense. The mis- 

 tletoe is a parasitic plant, the louse a parasitic animal. 



PARI'ETES. A name given to parts which form the inclosure or 

 limits of different cavities of the body, as the parietes of the 

 cranium, chest, &c. 



PAROT'ID. ('About the ear.') The largest of the salivary 

 glands, seated under the ear and near the angle of the lower 

 jaw. It secretes saliva. 



PATHOL'OGY. The branch of medicine whose object is the 

 knowledge of disease. It has been defined ' diseased physiol- 

 ogy,' and 'physiology of disease.' It is divided into general 

 and special. The first considers diseases in common; the 

 second the particular history of each. It is subdivided into 

 internal and external, or medical and surgical. 



PELVIS. The part of the trunk which bounds the abdomen 

 below. 



PERIODONTI'TIS. Inflammation of the membrane that lines the 

 socket of a tooth. 



PERIOS'TEUM. The periosteum is a fibrous, white, resisting 

 medium, which surrounds the bones everywhere, except the 

 teeth at their corona? (crowns), and the parts of other bones 

 that are covered with cartilage. The external surface is 

 united, in a more or less intimate manner, to the adjoining 



