EXPLANATIONS OF TERMS. 325 



Lens, any circular transparent body, with either convex or concave surfaces, for the 

 purpose of collecting or dispersing the rays of light. 



Locomotion, motion from place to place. 



Macerate, to soak a substance in any liquid, till its texture is softened. 



Marsupial Animals having a pouch or bag (marsupium) for containing their 

 young after jirth are called Marsupial animals; in this work they are all 

 arranged under one order, Marsupialia, but have been usually distributed 

 among the other orders. 



Mastication, the act of chewing the food and mixing it with saliva. 



Membranes, thin, broad expansions of animal substance, covering all the important 

 organs, and lining all the organs and cavities in the bodies of animals. Thus 

 the nose is lined by the Schneiderian or pituitary, and the eye covered by the 

 conjunctive membrane ; the stomach and bladder are each formed of several 

 membranes laid together. 



Menstruum, a dissolvent ; any substance in which another substance may be dis- 

 solved. 



Molares, Molar teeth, the grinders or double teeth, p. 27. 



Mucus, a viscid animal fluid ; such as the phlegm which is poured out from the 

 nose, or raised up from the throat in common colds. 



Multivalved, having many valves or shells ; applied to some shell-fish, as the sea 

 urchin, sea-egg, &c. 



Muscles (in Anatomy), bundles of fibrous flesh, fixed by tendons or sinews to the 

 bones, and serving to move them one upon another at their joints. In the mam- 

 malia, birds, and some reptiles, they are of a red color ; in other animals, for the 

 most part, white. They constitute the greatest portion of the flesh of animals, 

 and are the parts principally used as food. 



Nectariferous, bearing or producing honey ; applied to certain parts of plants from 

 which honey is collected. 



Nidus, a nest; any place where the eggs of animals are deposited for hatching. 



Nitrogen or jfzote, one of the gases which compose atmospheric air : its qualities ar 

 negative, and its principal use peems to be merely to dilute the oxygen. 



Nitrous oxyde, a gas composed of oxygen and nitrogen in different proportions from 

 those in which they exist in atmospheric air ; remarkable for its power of in- 

 toxicating and exhilarating those who breathe it. 



NympfuB, nymphs, insects in their second or chrysalis state. 



(Esophagus, the gullet ; the passage through which the food passes from the mouth 

 to the stomach. 



Oviparous, producing young by means of eggs. 



Oxygen, .vital air ; the principle upon which atmospheric aii depends for its power 

 of supporting life and combustion. It forms also one of the component parts of 

 water. 



Pachydermatous, thick-skinned ; belonging to the order Pachydermata. 



Palpi, organs situated near the mouth of some insects, resembling in some degree 

 the antennae in their structure. 



Papier machi, chewed paper. 



Papilla. The terminations of the nerves in the skin and other organs of sense are 

 supposed to form little eminences, which axe called papilla. 



Papion a perruyue, baboon with a wig. 



Parachute, a machine often attached to an air-balloon, and constructed so as to 

 open like an umbrella, and break the fall of a person descending from any great 

 height in the air. 



Passerine, belonging to the order Passeres, or birds of the sparrow kind. 



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