A text-book of physiology for medical students and physicians . ood orother circulating liquid up to a cer-tain optimum temperature. On theheart of the cold-blooded animal thisrelationship is easily demonstratedby supplying the heart with an arti-ficial circulation of Ringers solu-tion, which can be heated or cooledat pleasure. The rate and force ofthe beat increase to a maximum,which is reached at about 30° C.(see Fig. 247). Beyond this opti-mum temperature the beats decreasein force and also in rate, becomingirregular or fibrillar before the heartfinally comes to rest. Newell Mar-tin* has s
A text-book of physiology for medical students and physicians . ood orother circulating liquid up to a cer-tain optimum temperature. On theheart of the cold-blooded animal thisrelationship is easily demonstratedby supplying the heart with an arti-ficial circulation of Ringers solu-tion, which can be heated or cooledat pleasure. The rate and force ofthe beat increase to a maximum,which is reached at about 30° C.(see Fig. 247). Beyond this opti-mum temperature the beats decreasein force and also in rate, becomingirregular or fibrillar before the heartfinally comes to rest. Newell Mar-tin* has shown the same relation-ship in a very conclusive way uponthe isolated heart of the physiological limits the rateof beat rises and falls substantially parallel to the variations intemperature as is shown by the chart reproduced in Fig. 248. Theaccelerated heart rate in fevers is therefore due probably to the * Martin, Croonian Lecture, Philosophical Transactions, Royal Society,London, 174, 663, 1883; also Collected Physiological Papers, p. 40, Fig. 247.âTo show the effect oftemperature on the rate and force ofthe heart beat. Contractions of theterrapins ventricle at different tem-peratures. Kymograph moving atthe same speed. At 30° the rate isstill increasing, but the extent of con-traction has passed its optimum. 592 CIRCULATION OF BLOOD AND LYMPH. direct influence of the high temperature upon the heart itself. Thesame observer determined experimentally the upper and lowerlethal limits of temperature for the mammalian heart. The experi-ments were made upon cats hearts kept alive by artificial circu-lation through the coronary arteries.* It was found that the high-est temperature at which the heart will beat is about 44° to 45° C, fl 1 | 1 â * â fS! V Ss- \ \ { \ \ \ \ / / , / / / f * 1 lii i 1 *** \ \ j( 41 31 i ; â t * . * »» i » : i - toi* sir«â /*itLt ccletiizsz (7 I? 6/ it 1/etii 60 U> so £t> toil 19IfISCIIStoU ⢠o B
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