101* 



KXTKNT. 



ion 



persons by an injudicious employment uf them agent*, than in those 

 of the lung*, from common cold to the more serious and fatal 

 flection* of them rital organ*. The slight nature of many of the 

 common maladies of the throat and lung*, anil the fatality of con- 

 sumption, winch is generally though most erroneously regarded as an 

 affection of the lungs themselves, while it ia truly an affection of the 

 whole constitution, have led to a degree of interference with the treat- 

 ment of diseases of these organs not attempted in any other oases, as the 

 multitude of popular remedies for couglu, colilt, and funtumiiliont attest. 

 A certain exhalation from the internal surface of the lungs and air- 

 passages constantly goes on in a state of health any considerable 

 diminution or augmentation of this secretion may require the assist- 

 ance of medicines to raise it to the proper quantity in the one instance, 

 or to evacuate the superfluity and repress the tendency to its excessive 

 formation in the other. The chief causes which lead to diminished 

 Mvn-tion are inflammation and spasm hence at the commencement of 

 inflammatory affections of the air-passages and of the lungs the inner 

 membrane is dry, and by the stethoscope what is called the crepitating 

 rdle is heard ; in asthma and hooping-cough, while the spasm lasts, 

 there is an absence of secretion, which becomes abundant when the 

 spasm yields. 



To obviate these states very different means must be employed 

 from what are necessary in the later stages of an inflammatory affection, 

 or where there was extreme relaxation of the vessels of the lungs, and 

 the exhaled fluid redundant in quantity. One of the terminations of 

 inflammation being by effusion, when the increased action of the 

 vessels has lasted for some time a state of the lungs occurs which is 

 precisely the reverse of what it was before, and an extreme quantity 

 of mucus obstructs the access of air to the blood circulating through 

 the cells of the lungs : if this continue to accumulate, suffocation must 

 follow. Too great an accumulation sometimes takes place, especially 

 in elderly people, not from excessive secretion but from deficient 

 absorption. 



These are a few of the different states for which expectorants are 

 used, but much circumspection is required to accommodate the means 

 to the end. Where there is decided inflammation the best expectorants 

 are those which lessen the inflammatory state, such as venesection and 

 nauseating doses of tartrate of antimony or of ipecacuanha, and the in- 

 halation of the vapour of warm water, simple or medicated, by means 

 of Mudge's inhaler. But as the use of any such instrument requires 

 considerable exertion of the respiratory organs, where the inflamma- 

 tion is violent it is inadmissible, as the lungs must be kept in as 

 tranquil a state as possible ; but the head may be held over a basin of 

 warm water, the vapour of which will be received by the lungs in the 

 ordinary course of respiration. 



When the inflammation has subsided, the more stimulating expec- 

 torants may be used. Where there is first spasm hindering secretion, 

 and ultimately an excessive exhalation which must be cleared away, 

 a combination of a sedative or antispasmodic medicine with the 

 expectorant is best. 



These are the principles which should regulate our choice in the 

 more acute affections of the chest; but as no set of organs are so 

 subject ,to chronic disorders as the lungs and their appendages, we 

 frequently have recourse to expectorants to alleviate many of the 

 symptoms attendant on them. 



Lessening the tendency of blood towards the lungs, and directing it 

 more towards the skin, is of service both in acute and chronic 

 affections of the chest. Hence bathing the feet in water on the first 

 feeling of an attack of cold, followed by antimonials or other diapho- 

 retics, is of much utility, if the patient go into a warm bed imme- 

 diately ; while on the same principle, the use of flannel next the skin 

 is the best preventive, and is indispensable for all delicate persons, 

 particularly if predisposed to diseases of the lungs. 



EXPLOSION is the sudden displacement of a considerable volume 

 of air, or of any gaseous particles, accompanied by a loud report. 



In the well-known experiment with a glass cylinder having one end 

 covered with a thin bladder tightly bound about it, the column of air 

 incumbent on the bladder suddenly descends into the vessel on the 

 rupture of the bladder when the air beneath is withdrawn by means 

 of an air-pump ; and the collision of its particles with one another or 

 with the sides of the vessel produces the vibrations which cause the 

 perception of sound. The particles of steam, in a state of high 

 elasticity, when suddenly liberated by the bursting of the vessel in 

 which they are contained, produce also a loud report by their collision 

 with the atmospherical particles about them, or by the rush of air into 

 the rarefied space which they have quitted. The elastic gases liberated 

 on the application of fire to gunpowder in a tube, and the heat pro- 

 duced at the same time, create a rapid displacement of the particles of 

 the surrounding atmosphere ; and these as rapidly falling back into the 

 vacuum within and about the fire-arm, cause a loud report by their 

 collisions. A fulminating powder is the cause of a like explosion being 

 produced, by means of the gases which are set free in consequence 

 merely of the friction of the particles. 



The explosions which, in the atmosphere, accompany a flash of 

 lightning, are also ascribed to a similar displacement and subsequent 

 rush of air into the vacuum produced. 



For the explosion produced by chemical combinations, see DETO- 

 JTATIOS. 



EXPONENT; EXPONENTS, NOTATION Of. In the alge- 

 braical expression o , x ia called the exponent of a. If we were 

 strittly to preserve the most ancient meaning of the term, j would 1? 

 called the exponent of the whole symbol a* : but it is usual to call j 1 the 

 exponent of a, and the logarithm of a* . 



From the time of Descartes it has been usual to employ exponents 

 in abbreviation of repeated symbols of multiplication : but this was 

 only the (beginning of a series of extensions which have mad<- :!..- 

 theory of exponents a fundamental part of analysis. Beginning with 

 the simple substitution of a* instead of a x a, a* instead of a x a x a, 

 and so on, we have a succession of new symbols suggested by the 

 processes of algebra, namely, that a 1 should stand for a, a for unity, 







a~* for the reciprocal of a*, and a * for the nth root of the mth power 

 of a. These conventions being made, the common algebraical theory 

 of exponents is complete; and the student will find in works on 

 algebra an account of the manner in which the necessity for these 

 extensions appears. The theory of logarithms flows naturally from 

 this notation and the binomial theorem. 



Looking at the notation of exponents in another point of view, we 

 see that a 1 , or a, signifying the performance of a certain op. i 

 on the unit, a 1 , or an, signifies the repetition of the same op< 

 upon a itself ; a 3 denotes the repetition of the same operation upon a 1 , 

 and so on. Hence by analogy, whenever, in the higher parts of 

 analysis, <j>x signifies an operation performed upon *, <f> 'x signifies the 

 repetition of the operation upon fur. Thus if 0* signify 1 + 2x, then 



<t>*x is 1 + 2 (1 + 2*) or 8 + 4*. 

 <ffx is 1+2(3 + 4*) or 7 + 8*. 4c. 



It appears by reasoning analogous to that which establishes th'e 

 meaning of exponents in algebra, that <(P x must stand for x itself. 

 Also <t>~'x must signify the operation inverse to (or which destroys the 







effect of) <t>x; thus if $x signify xf, <t>~'x must be */x. Also $* s 

 means that operation which performed tunes in succession, gives the 

 same result as <t>x performed m times. 



The Differential Calculus and the Calculus of Differences furnish 

 striking examples of the notation of exponents. As soon as the 

 student arrives at the higher parts of these subjects, he should pay 

 particular attention to the structure of the notation, and in (ar- 

 ticular to the meaning of those theorems in which the symbols of 

 operation are separated from those of quantity. 



EXPORTS. [IMPORTS and EXPORTS.] 



EXTENT (Lat. extenta) is a writ of execution (sometimes called an 

 e.i'tendi facias), which is directed to the sheriff against the body, lands, 

 and goods, or the lands only, of a debtor ; and it is also used as signi- 

 fying the act of the sheriff or officer upon the writ itself. 



The king by ancient prerogative is entitled to this writ, either in 

 chief or in aid, for the purpose of obtaining satisfaction of debts origi- 

 nally due to him or assigned to the crown. The writ of extent in <-l<nj 

 is an adverse proceeding by the king for the recovery of his own debt, 

 and in which he is the real plaintiff. The writ is issued out of the 

 Court of Exchequer ; and the sheriff, for the purpose of executing it, 

 may break open the defendant's doors, when purposely closed, either to 

 arrest him or to take his goods. If, however, the defendant cannot be 

 found, or is not meant to be arrested, the sheriff impanels a jury to 

 inquire as to the debtor's lands and tenements, goods, and chattels ; 

 and after the inquisition is made, the lands then become bound to the 

 crown until the debt is satisfied. The writ of extent in aid is also sued 

 out at the instance and for the benefit of the crown against the 

 of a crown debtor : in this proceeding the king is the nominal plaintiff 

 only. The writ is in effect an extent in the second degree, ami in 

 to obtain it an extent pro formd is sued out against the debtor to the 

 crown, upon which an inquisition is taken ; and if it be thereupon 

 found that another person is indebted to him, the Court of Exchequer, 

 on an affidavit to that effect, and also to the effect that the crown debt 

 is in danger, will grant a fiat or warrant for an immediate extent in aid. 

 Under this writ, the body of the defendant may in strictness be taken 

 in execution as well as his lands, tenements, goods and chattels, &c. ; 

 but where there are effects sufficient to satisfy the debt, the court 

 seems generally disposed to give the defendant his discharge. 



On the return of the writ of extent in chief or in aid to the court 

 whence they are issued, an order is endorsed on the back of it, " that 

 if no one shall appear and claim the property of the goods, 4c., men- 

 tioned in the inquisition, on or before that day se'nnight, a writ of 

 venditioni exponas shall issue to sell the same." If the produce of the 

 goods sold be not sufficient to pay the debt, the court will make an order 

 for the sale of the debtor's lands under the 25th George III., c. 85. 



There are various means of resisting the execution of the above 

 writs, on the ground of informality or want of title in the crown ; 

 which may be referred to in the second volume of Mr. Tidd's work on 

 the practice of the superior courts. 



Upon the subject of extents for the subject see Ei 



When lands are delivered over to a creditor upon an extent, a reason- 

 able but not the real value is set upon them ; and the effect is the same 

 as if the creditor took a lease of the lands until his debt is sati^t 



(Coke on Littleton; Tidd's Practice; Blackstone's Commmtarici, 

 Kerr's edition.) 



