. Arthur and Fritz Kahn Collection 1889-1932. Kahn, Fritz 1888-1968; Kahn, Arthur David 1850-1928; Natural history illustrators; Natural history. Fi){. 2. The circulatory system among higher animals 'I'lic aiiri( Ics and c) arc placod upoii thc \'nitri(l(>s so tliat tlie blood can 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
. Arthur and Fritz Kahn Collection 1889-1932. Kahn, Fritz 1888-1968; Kahn, Arthur David 1850-1928; Natural history illustrators; Natural history. Fi){. 2. The circulatory system among higher animals 'I'lic aiiri( Ics and c) arc placod upoii thc \'nitri(l(>s so tliat tlie blood can 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 anim
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