Title: Arthur and Fritz Kahn Collection 1889-1932
Identifier: arthurfritzkahn_04_reel04 (find matches)
Year: [1] (s)
Authors: Kahn, Arthur and Fritz
Subjects: Kahn, Fritz 1888-1968; Kahn, Arthur David 1850-1928; Natural history illustrators; Natural history
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Contributing Library: Leo Baeck Institute Archives
Digitizing Sponsor: Leo Baeck Institute Archives

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Fi)(. 2. The circulatory system among higher animals 'I'lic aiiri( Ics f.i and c) arc placod upoii thc \'nitri(l(>s so tliat tlie blood can r.tpidly aiid casily tili tlie ventricles through all thc organs of thc body, and froni ihose agnin back to thc hcart. Thc j)ath of thc blood is dividcd into two cir- cuits, and forms a figurc 8, thc hcart bcing at thc point where the two circlcs nicct (Fig. i). By this mcans thc work of thc hcart is lightcncd, sincc it has to pump thc blood through half thc total circuit only bcforc its return to the hcart. The one lialf of the (irculatory path car- ries the blood from thc hcart to the lungs and back from these again to the hcart. (This is called pulmonary c i r c u 1 a - tion, or, because it is the smallcr, thc Icsscr (irrulation.) Thc othcr, largcr j)ath, rarrics thc blood into all the remai- ning j)arts of thc body, and is thcrcforc called the greater, or systemic cir- culation. During thc circulatlon through thc lungs thc blood takes up oxygcn from the inspircd air. This gas passes from the air passages oi thc lungs through thc walls of thc tiny capillarics into the blood. Car- ried by this it passes first into thc hcart and then on to the body. The oxygcn unites with the carbon of the food in the Organs which arc doing work. By this rombination encrgy is produred of which thc more considerable part appcars as hcat; this process is thcrcforc called the Combustion of Food. As the result of the combination of oxygcn (Og) and carbon (C; carbon-dioxide (COg) is produ- ced, which in considerable concentration acts as a poison. It is thcrcforc carried away from thc active organs to the hcart, and thcnce to the lungs, so that it may be thcre exchanged for fresh oxygcn. The heat ;)rodu( cd by (ombustion is thc (ause of thc tcmperature of thc blood, (37^ C or 98-40F;. hl the lovver animals the heart takes a shape like that in Fig. i. It appcars as a thickened middle portion of the two blood-vessels at thc transition from systemic to pulmonary circulation, and consists consequcntly of two portions, The first, through which flows thc blood containing carbon-dioxide is the carbon- dioxide portion (black); the second, through which flows the blood containing oxygenated blood on the way from the lungs to the body, is the oxygcn part (white in the diagram). Each half of the heart is again dividcd into two parts. The Chamber into which the blood flows (a and c) remains undevclopcd bccausc it is a receptacle for blood mercly, and thcrc- forc has to perform but little work. It is named the Auricle. On the other band, the portion which drives the blood on its way is, because of its greater functional activity, more highly developcd. It is called the Ven- t ricl e (b and d). In higher animals these simple rclations are somewhat more com- plicatcd, in that the auricles are placed right on top of the ventricles, so that the blood can rapidly and casily fill the ventricles. Tlie blood then traverses the route shown in Fig. 2. Because the higher animals are bilaterally symmetrical and posscss two lungs, the circulation through the lungs is dividcd into two parallel cir- cuit s. If one has obtained by means of Figs i and 2 a general idea of the plan of the circulation in the higher animals, one is in thc Position to follow in Fig. 3 the cir- culation of the blood in the human body in its fundamental schematic outlines. f The blood leaves the left ventricle (i) by means of the large artery called the Aorta, and climbs to the top of thc arch of thc aorta (2), and thcnce by 3a into the lowcr and by 3b into thc uppcr parts of thc body. There it divides up in the capilhirics, 4a and 4b, givcs up oxygcn and rcturns through the venae cavae, 5a and 5h, back into the right auricle . (6). Thcnce, it flows into thc right . ventricle, and, drivcn forward by the contraction of thc latter's muscular wall, rises in the puhnonary artery (8\ and passes either via 9a into the right or via 9b into thc left hing. After giving up carbon-dioxide and receiving oxygcn ( loa and lob) it rcturns via the pulmonary veins (iia and 11b) back into tlie left auricle (12), thence to pass down into the left ventricle (i) and again from therc to be drivcn into the aorta. So that thc blood may bc drivcn on its way through thc hcart ever forward and never backward, valves are inscrtcd just as thc cnginccr inserts them in a pump. They arc "flap-valves", of a mcmbranous tissuc, flapping into positions to check any flow in the vvrong dircction. In thc small picturcs I—^IV of thc colourcd diagram (Fig. 4) arc shown thc course of thc blood through tlic heart, the four phases of thc heart beat and the action of thc valves. I. Both thc auricles (A) fill thcmsclves: thc right auricle (bluc) with blood loadcd with carbon-dioxide from thc body, and thc left auricle (red) with oxygenated blood from thc lungs. Thc blood in the • superior vena cava comes from thc u;)i)cr parts of thc body, head and arnis, while that in thc inferior vena cava comes from the trank and thc legs. One ;)uhn()nary vein comes from thc right and thc othcr from thc left lung. Because the valves in the floor of thc auric Ics, the mcmbranous valves, are shut, thc blood does not immc- diatcly pour into the ventricle but fills the auricles. II. The walls of the auricles, under thc influence of the rising pressure of blood, have contracted ancd drivcn the blood through the Auriculo-ventricular valves into the ventricle (B) bencath. Thercafter, here also, when thc Stimulus of thc rise in pressure has reached a certain height, the walls of the ventricles, which consist of muscle fibres, contract. III. The mass of blood i.s sct in motion by the pressure of the ventricle wall. The auriculo-ventricular valves, which open only in the direction auricle-to-ventriclc, slam back, and shut off the blood from flowing back into the auricle. At the same time the semilunar valves (C) inserted between ventricles and artcrics are opcned by the pressure of thc blood, and, bcing presscd flat against the walls, allow the blood to flow into thc artt^ics, from the right heart into thc pulmonary artery and

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