I N T 



is not what I blame ; on tVio contrary, I think it may be 

 urcful to efTace, by an agreeable dance,the melancholy impref- 

 Cons left by the events of a grand ferious opera ; and I fee 

 plainly that the fubjeft of this dance ihoidd have no coii- 

 netlion with the piece ; but what ofTendi me, continues the 

 citizen of Geneva, is tliat tliey delboy all the intereft that 

 has been excited, and render each adTt a new piece." We 

 Tuppofe he means that the ballet lliould be given at the end, 

 not in the middle of the opera. 



INTERMITTENT, a thing which ceafes its aaion for 

 fome time ; whicii time is called the interval. 



IxTi'KMiTTEKT, in Medic'wr, any animal motion or ac- 

 tion, wliich ceafes and returns at intervals. The period of 

 eeffation is termed the interval, or iiitermijjicn. 



Thus thofe fevers which, after continuing feveral hours, 

 altogether go off, and again return at certain intervals, as of 

 ■one, two, or three days, are called intermittent fevers, in 

 •ontradillinftion from thofe which go through their courfe 

 with httle variation, or wiih regular diminution and aggra- 

 vation only ; the former being called continued, the latter re- 

 mittent fevers. See Fever and Ague. 



Various other diforders, belides the acute fevers jufl men- 

 tioned, put on the intermittent form ; fuch as head-ache, 

 efpecially the hemicranin, or head-ache of one fide of the 

 head, the megrim, and fometimes the tic douLureux ; and 

 pains, feated in various other parts of the body, as in the 

 liver, bladder, uterus, &c. It is extraordinary, and does 

 not eafily admit of any explanation, that, in parts of the 

 body, fuffering fevcre organic difeafe, and aftually much 

 injured in their ftruclure, the pain coniiefted with this dif- 

 order fometimes becomes reijularly intermittent with intervals 

 of abfolute freedom from the diftrefs ; while of courfe no 

 variation can have occurred in the morbid ilrufture. Such 

 intenniflions we ba»e witneffed in cancerous and ulcerated 

 conditions of the womb ; and, in fuppuration in the brain. 

 But, iiideed, it is equally difficult to account for the faft in 

 all inftances ; and no fpeculations have yet enabled us to ex- 

 plain, why the velTels of any part, (as of the fupra-orbital 

 notch, in the cafe of megrim,) or of the whole fyftem, (as in 

 ague,) ftiould take on an extraordinary action at regular but 

 diltant periods, and continue only their ordinary aclionin the 

 intervals : whether the parts be actually difeafed in ftrufture 

 or not, the periodical recurrence and eeffation of increafed 

 ▼afcular action is equally inexplicable. Dr. Darwin has in- 

 genioufly endeavoured to refer thefe periodical changes to 

 the influence of our diurnal habits, in regard to aftivity and 

 fleep, exhauftian of fenforial power and invigoration, and 

 to the diurnal periods of heat and cold, hght and darknefs, 

 &c. upon all the actions of our frame. That thefe circum- 

 ilauces greatly influence the operations of the animal body, 

 cannot be doubted : and were all the periods of action and 

 intermilTion diurnal only, we might admit the generahzation 

 as correct. But it is not eafy to difcover how the very fre- 

 quent intermijffions of difeafe, which continue for tertian pe- 

 riods, that is, during an interval of forty-eight hours, and 

 ftill more tliofe which continue for quartan periods, of 

 feventy-:wo hours, can be referred to this general law. Sec 

 Darwin, Zoonomia, vol. i. feft. j6. 



The bark of the cinchona, and fome other bitter vegetable 

 fubftanccs, it is well known, pollefs a conliderable degree of 

 power, when adminiftered during the intcrmiffions, for pre- 

 venting the recurrence of difcafes of this clafs. But a reme- 

 dy has been added to the lift of the materia meflica, which 

 fefems to have a fpecific virtue of arrelling all intermittent affec- 

 tions r we mean the arfenic, which had long been ufed as an 

 empiric noftrum, under the appellation of the " taftelefs 

 ague-drop," but whicb was firft prepared in a fafe and ma- 



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nageable form by the late Dr. Fowler, of Vork, »nd i* now 

 introduced into the pharmacopeia of the College of Phyfi- 

 cians of London. This medicine has not only been adnii- 

 nillered with decided benefit in intermittent fevers ; but 

 alfo in the intermittent head-ache and megrim, with the moll 

 marked fuccefs. And we have found it, in more inilances 

 than one, fpeedily arrefl the intermitting paiu.; in difeafed 

 uterus, and other organic painful difcafes. In a word, 

 arfenic appears to have a fpccilic remedial powei- over perio- 

 'tlical difordcrs. But in cafes of organic difeafe, its infiuenco 

 is of courfe confined to the periodic pains coiincfted with 

 them, and is not exerted upon the fixed and continued af- 

 feftion. 



The term intermittent js alfo applied to the pulj'e, when, 

 after an indefinite number of beats, it flops during the time 

 of one pulfation, or lofes a ttroke. Tiiis is fometimes a 

 formidable fymptom, when connected with other figns of 

 affedtiun of the brain, or of the heart itfelf ; but it is more 

 commonly of minor import, being conneftcd wiili indigef- 

 tion, and a general irritability of the fyllem, and is ro- 

 movable by correcting the tlate of the floniach and other ori. 

 gans concerned in the chylopoetic procefs. See Pt'L.SE. 



INTERMITTING Spuin-g.s, in Natural Hiftory, or 

 ebbing and flowing wells, are phenomena which attracted 

 a great deal of attention in former times, and feveral works 

 on natural philofophy contain explanations of the principles 

 on which they might, by a proper application of the fyphon, 

 be made, by art, fo as afterwards to be felf-adting : it can 

 fcarcely be doubted but fome of the intermitting fprings 

 were natural, or produced their ebbing and flowing or inter- 

 raiflion, without the aiTillance of art, perhaps that on the 

 N.N.W. fide of TidefvveU town in Derbyftiire, which for- 

 mei-ly exiited and gave the name to the town, may have been 

 of this number; and perhaps alfo Laywell fprings at Brix- 

 ham, in Devonfhire, may have been natural ; but Mr. FiU-ey, 

 in his recent Report on Derbyfliire, (vol. i, p. 28S.) flates 

 the ebbing well at Barmoor, between Caltleton and Chapel- 

 en-le-Frith, on the flvirt of Peak forefl, in Derbyfhire, to 

 occupy the fcite of an old Itone-quarry, in the flrll limeftone 

 rock, and to be evidently the work of art ; he alfomentions 

 an artificial well of tins kind lately made in the parifh of 

 Chapel-en-le-Frith. See Spring. 



INTERNAL Angles, are all angles made by the fides 

 of any right-lined figure within. 



In a triangle, as KLM [PlateVlll. G€nmetry,J:g. 103.) 

 the angles L and M are particularly called internal and opps- 

 Jite, in refpea of the external angle I KM, which is equal 

 to them botii. See Internal Angles. 



Interval ^ngle, is alfo applied to the two angles formed 

 between two parallels, by a line interfecting thoie parallels, 

 on each fide the interfering line. 



Such are the angles x and y, and * and s {Plate VIII. 

 Geometry, Jg. 104.) formed between the parallels OP and 

 Q R, on each fide of the interfcfting line S T. 



The two internal angles are ahvays equal to two right 

 angles. 



Internal and Ofpofite Angles, arc alfo applied to the two 

 angles 2 and x, formed by a Inie cutting two parallels. 



Thefe are refpeftiveiy equal to A and u, cgUcd the ex- 

 ternal and oppolite angles. 



Internal AJfeBion, Denomination, Ear, Modes, Ortho- 

 graphy, Place, Sen/e. See the fubftantives. 



Inteknal Plans, in Mining, fignify, according to M. 

 Werner (New Theory of Veins, Tranfl. p. 194.1, the in- 

 terna] drawings, or feftions as they are called in this country, 

 of, the mines and the llrata, or of rocks in which they occUr. 

 Se^ions of particalar diftridts, forntrd into tablets inlaid 

 N n 7 nith 



