////: iir.uiT. 499 



" Tbo socoiid extends from all parts of tlio body to the lungs, and curries 

 dark Mood. 



" The third passes from the majority of the orgatis towards the canal 

 carrying dark blood, in which it terminates ; it conveys the white blood or 

 lymph. 



" The red-blood and dark-blood canals boar the greatest analogy to each 

 other. Both are simple in their middle portion, which alternately dilates 

 :u nl contracts to impress upon the blood the movement necessary to life. 

 P> >th present at their extremities innumerable ramifications, which ultimately 

 join each other; so that the fluid they carry passes from one to the other 

 in a constant and circular direction. Both are composed, at their origin, 

 of vessels in which the blood moves in confluent columns : these are the 

 : and in their terminal part, of vessels in which the same liquid is 

 spread in divergent columns : these are the arterit*. 



" The canal for white blood is composed of a single order of vessels, the 

 lfmfkatic$ : converging tubes, whose common trunk opens into the circulatory 

 canal that results from the abouchement of the red and dark blood canals ; 

 the relation it affects with these latter is that of a tangent with its cir- 

 cumference." Sajiji' //. 



These three canals constitute the circulatory apparatus. 



This apparatus therefore comprises : 1, The heart, a central organ, 

 charged to propel the blood ; 2, A system of centrifugal vessels, the arteries, 

 which carry the blood from the heart into the different organs; 3, A 

 system of centripetal vessels, the reins, which bring the nutritive fluid to 

 the heart ; 4, The lymphatics, an accessory centripetal system, destined to 

 convey the lymph into the blood-vascular circle. 



la many anatomical works, the study of this apparatus the heart, 

 arteries, veins, and lymphatics, is designated " angiology." 



1'IIiST SECTION. 



Tin: HKAKT. 



TIIK hi.-tory of the heart comprises : 1, A general view of thf or^an : 

 J. The. study of its external conformation ; 3, Its interior ; I. Its strnctmv : 

 5 A .1 -eription of the pericardium, the serous cavity containing it ; 6, A 

 j_'l:inc(j lit its physiology. 



1. The Ifrart as a Whole. (Figs. 230, 234, 258, 259.) 



,/ x/ t -. /</*. The heart, the central portion of the circulatory 

 apparatus, is a hollow muscle, whoso cavity is divided l.y a thick vertical 

 septum into two perfectly indQP&lde&t pouches. Of tlu.-e two contractile 

 pouches, one placed oil tin- track of the dark blood, propels it into the IUIIL,'-; 

 the other, situated on the course of the red blood, distributes it to all parts 

 of the |.idy. 



Each of these is subdivided into two Mipcrpo>cd compartments by a 

 ;lar constriction, ut which is a membranous valve that at certain fixed 

 periods is elevated, and then forms a complete hori/ontul partition extended 

 IH -tweeii the two compartments. 



The superior compartment receives the convergent or coutri|N-tal portion 



2x2 



