260 



CIRCLE 



CIRCULATION 



radius. Thus the circular measure of 180 is 

 or 3-14159, &c., 90 = TT, 60 = f TT, 45 = J TT, and 

 so on ; and since IT is a fixed number, any angle is 

 thus represented absolutely, and not as a part or 

 multiple of another angle i.e. an abstract number 

 will as exactly denote an angle as it does the length 

 of a line. If we say 6 = 3, then in degrees = 3 

 x (57 17' 45") ; if <f> = ^, then = x (57 17' 45") 

 sexagesimally. For the squaring or quadrature, of 

 the circle, see QUADRATURE ; for the circles of the 

 sphere, see ARMILLARY SPHERE ; see also MURAL 

 CIRCLE. 



Circle, MAGIC, a space in which sorcerers were 

 wont to protect themselves from the fury of the 

 evil spirits they had raised. This circle was 

 usually formed on a piece of ground about nine 

 feet square (in the East seven feet appears to 

 have been considered sufficient), in the midst of 

 some dark forest, churchyard, vault, or other lonely 

 and dismal spot. It was described at midnight in 

 certain conditions of the moon and weather. In- 

 side the outer circle was another somewhat less, in 

 the centre of which the sorcerer had his seat. The 

 spaces between the circles, as well as between the 

 parallel lines which inclosed the larger one, were 

 filled 'with all the holy names of God,' and a 

 variety of other characters supposed to be potent 

 against the powers of evil. Without the protection 

 of this circle, the magician, it was believed, would 

 have been carried off by the spirits, as he would 

 have been had he by chance got out of the 

 charmed space. Another figure which, described 

 upon the ground, could bar the passage of a demon, 

 was the pentagram. Readers or Faust will remem- 

 ber its effect upon Mephistopheles. 



Circles, STONE. See STONE CIRCLES, STAND- 

 ING STONES, STONEHENGE, CALLERNISH. 



Circuits. See ASSIZE. 



Circular Notes are bank-notes specially 

 adapted for the use of travellers in foreign countries ; 

 and being, in fact, bills personal to the bearer, they 

 are believed to be more safe as travelling money than 

 ordinary notes or coin. Circular notes of the value 

 of 10 and upwards are furnished by or through the 

 chief banking-houses. Along with these notes is 

 given a ' letter of indication. ' This letter ( a 

 lithographed form in French ) is addressed to foreign 

 bankers, requesting them to pay the notes pre- 

 sented by the bearer, whom they name, and to aid 

 him in any way in their power. On the back of 

 the letter there is a long list of foreign bankers, 

 extending all over Europe, any of whom will cash 

 one of the circular notes on being presented and 

 indorsed by the bearer. In paying these notes the 

 money of the country is given according to the rate 

 of exchange, and free of any charge for commission. 

 For security, the letter and the notes should not be 

 carried together, in case of their being stolen or lost. 

 A corresponding certificate issued by the bankers in 

 the United States for the use of travellers, is called 

 Letter of Credit. See CREDIT (LETTER OF). 



Circular Numbers are numbers whose powers 

 end on the same figure as they do themselves : 

 such are numbers ending in 0, 1, 5, 6. 



Circulating Library See LIBRARY. 



Circulation, in Anatomy and Physiology, is 

 the term used to designate the course of the blood 

 from the heart to the most minute blood-vessels 

 (the Capillaries, q.v.), and from these back to the 

 heart. To simplify the consideration of the subject, 

 we shall consider ( I. ) the General Anatomy, (II.) 

 the Comparative Anatomy, ( III. ) the Phvsioloev 

 and (IV.) the History. 



I. The organs of circulation consist of the heart, 

 arteries, veins, and capillaries. The course of the 

 blood through these organs will be best -elucidated 



Fig. 1. Diagram of Cir- 

 culating* System ( from 

 Leunis). 



by the aid of a diagram, which is equally applicable 

 for all other mammals as well as for man, and for 

 birds. The dark parts 

 of fig. 1 represent the 

 course of the impure or 

 venous blood, while the 

 lighter portions repre- 

 sent the course of the 

 pure or arterial blood. 

 Two of the four cham- 

 bers of the heart ( A and 

 C ) receive the inflowing 

 blood, and are termed 

 the auricles; while the 

 other two chambers 

 (B and D) drive the 

 blood to the lungs and 

 to the general system 

 respectively, and are 

 termed tlie ventricles. 

 The vessels that bring 

 blood to the auricles are 

 termed veins, and the 

 vessels through which the 

 blood is driven from the 

 ventricles are known as 

 Arteries ( q. v. ). We will 

 now trace the course of 

 the blood, as indicated 

 by the arrows of the 

 diagram, commencing 

 with the right auricle, 



A. The right auricle 

 contracting upon the 

 venous or impure blood 

 with which we suppose 

 it to be filled, drives this 

 into the right ventricle, 



B, through an opening 

 guarded by a triple (or 



tricuspid ) valve, which almost entirely prevents the 

 regurgitation of the blood from the ventricle into 

 the auricle. The ventricle, B, being now filled, 

 contracts, and as the blood cannot return into the 

 auricle, it is driven along the dark vessel, c, 

 which is the pulmonary artery, conveying the blood 

 to the lungs. At its commencement it is guarded 

 by crescent-shaped (semilunar) valves, which en- 

 tirely prevent the blood which has once been pro- 

 pelled into the pulmonary artery from re-entering 

 the ventricle. The pulmonary artery gradually 

 divides into smaller and smaller branches, which 

 ultimately emerge into capillaries freely distributed 

 over the interior of the air-cells of the lungs. There 

 the blood gives off carbonic acid gas, and absorbs 

 oxygen, becoming thereby 'pure.' The capillaries, 

 in which the blood is purified, gradually unite to 

 form larger vessels, and finally the blood is collected 

 into the pulmonary veins, which pour their con- 

 tents into the lef\_auricle, C. Thence it is pro- 

 pelled into the left ventricle, D, through an open- 

 ing guarded by a double ( mitral or bicuspid ) valve, 

 which entirely prevents the reflux of the blood. 

 The left ventricle contracts and drives its contents 

 into the large artery, e, or Aorta (q.v.), which 

 by means of its various branches supplies the whole 

 body with pure blood. From the aorta and its 

 various subdividing branches the blood passes into 

 the capillaries, J, H, Avhich occur in every part of 

 the system. In these capillaries it parts with its 

 oxygen to the tissues, and becomes charged with 

 the waste carbonic acid gas. The capillaries unite 

 into larger veins, and these gradually unite to form 

 two large trunks, a, b, the superior and inferior 

 vence cavce, which pour their contents into the 

 right auricle the point from which we started. 

 The diagram also shows how the venous blood from 

 the viscera, G, instead of passing directly into the 



