APE 



APH 



AORTA, in anatomy, called also arte- 

 ria magna, a large artery, arising with a 

 single trunk from the left ventricle of the 

 heart above its valves, called semilu- 

 nares, and serves to convey the mass of 

 blood to all parts of the body. 



After ascending a little upwards, its 

 trunk is bent, in manner of an arch, and 

 from this part it sends, in human subjects, 

 usually three ascending branches. This 

 is called the aorta ascendens. 



The descendens is that part of the 

 trunk, which,after the arch-like inflection, 

 descends through the thorax and the ab- 

 domen down to the os sacrum, and is 

 usually larger in women than in men. 

 The aorta hath four tunics, a nervous, a 

 glamlulous, a muscular, and a membra- 

 nous one. See AJTATOMY. 



APACTIS, in botany, a genus of the 

 Dodecandria Monogynia class and order. 

 No calyx; petals four, crenate, unequal; 

 germ superior; fruit. There is but a sin- 

 gle species, viz. the Japonica, atreefound, 

 as its name imports, in Japan. 



APALUS, in natural history, a genus of 

 insects of the order Coleoptera. Gen. 

 char, antennae filiform ; feelers equal, fili- 

 form ; jaw horny, one-toothed; lip mem- 

 branaceous, truncate, entire. There are 

 two species : quadrimaculatus ; rufous ; 

 head, and two spots on the shells, black ; 

 inhabits North America : bimaculatus, of 

 northern Europe. 



APARGIA, in botany, a genus of the 

 Syngenesia JEqualis class and order. Re- 

 ceptacle naked ; calyx imbricate ; down 

 feathery, sessile. There are 17 species. 



APATITE, in mineralogy, one of the 

 species of the phosphates, occurs in tin 

 veins, and is found in Cornwall and Ger- 

 many. Colours white, green, blue, and 

 red, of various shades. The primitive 

 form of its crystals is a regular six-sided 

 prism. Specific gravity between 2.8 and 

 3.2. When laid on ignited coals it emits 

 a green light, and is almost entirely solu- 

 ble in nitric acid. By rubbing it shews 

 signs of electricity. It was formerly con- 

 sidered as a species of schorl ; afterwards, 

 on account of its colour and crystalliza- 

 tion, it was arranged with beryll ; others 

 described it as fluor, but Werner soon 

 found that it was a new species. Its fal- 

 lacious resemblance to other minerals in- 

 duced Werner to give it this name, which 

 is derived from a-7, " to deceive." 



APE. See SIMIA. 



APETALOSE, or APETALOUS, among 

 botanists, an appellation given to such 

 plants as have no flower leaves. 



APEX, in antiquity, the crest of a hel- 



met, but more especially a kind of cap 

 worn by the flamens. 



APHJERESIS, in grammar, a figure by 

 which a letter or syllable is cut oft' from 

 the beginning of a word. 



APHJBRESIS, that part of surgery which 

 teaches to take away superfluities. 



APHELIUM, or APHELION, in astro- 

 nomy, is that point in any planet's orbit, 

 in which it is farthest distant from the 

 sun ; being, in the new astronomy, that 

 end of the greater axis of the elliptical 

 orbit of the planet, most remote from the 

 focus wherein the sun is. The times of 

 the aphelia of the primary planets may be 

 known by their apparent diameters ap- 

 pearing least ; as also by their moving 

 slowest in a given time. They may like- 

 wise be found by calculation, the method 

 of doing which is delivered in most astro- 

 nomical writers. 



Sir Isaac Newton and Dr. Gregory have 

 proved that the aphelia of the primary 

 planets are at rest. See Princip. prop. 14. 

 lib. 3. And in the scholium to the above 

 proposition they say, that the planets 

 nearest to the sun, viz. Mercury, Venus, 

 the Earth, and Mars, from the actions of 

 Jupiter and Saturn upon them, move a 

 small matter in consequentia with regard 

 to the fixed stars, and that in the sesqui- 

 plicate ratio of their respective distances 

 from the sun. 



APHIS, in entomology, a genus of the 

 Hemiptera order, which has engaged the 

 attention of naturalists for various rea- 

 sons : their generation exhibits a singular 

 and surprising phenomenon, and their in- 

 stinctive economy differs, in some res- 

 pects, from that of most other animals. 

 Linnaeus defines the generic character of 

 the aphis thus; beak inflected, sheath of 

 five articulations, with a single bristle a 

 antennae setaceous, and longer than the 

 thorax ; either four erect wings or none ; 

 feet formed for walking ; posterior part 

 of the abdomen usually furnished with two 

 little horns. Geoffroy says, the aphides 

 have two beaks, one of which is seated in 

 the breast, the other in the head ; this 

 last extends to and is laid upon the base 

 of the pectoral one, and serves, as that 

 writer imagines, to convey to the head a 

 part of that nourishment which the insect 

 takes, or sucks in, by means of the pecto- 

 ral beak. Gmelin enumerates about 70 

 species, all of which, and doubtless many 

 others, are found in different parts of Eu- 

 rope and America. They infest an end- 

 less variety of plants ; and it is believed 

 each species is particularly attached to 

 one kind of vegetable only ; hence each 



