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		Results        As each heart beat at a different rate in Dulbecco's Eagle Medium, the number of beats produced in the DMEM control after one minute was used as the base heart rate (BHR) for each heart. The base heart rates were consistently higher than those obtained in Howard Ringers (Howard) Solution (Table 1). All hearts in both groups beat faster than their base heart rates when transferred to the 0.1 mg/ml caffeine solution (Tables 1 and 2). The hearts in Group B were then transferred into the 0.2 mg/ml caffeine solution, and their heart rate increased again (Table 1). When the hearts were transferred into the 0.3 mg/ml caffeine solution, their heart rate was slower than it had been in the lower caffeine concentrations, although it was still higher than the base heart rate in DMEM (Table 1). Table 1. The heart rate in beats per minute (bpm) of Group B hearts tested in Howard Ringer solution, DMEM, and the caffeine solutions of concentrations 0.1mg/ml, 0.2 mg/ml and 0.3 mg/ml. The reaction of each heart to the various solutions is also shown as the percentage of the base heart rate (BHR) in DMEM. Group B Howard DMEM 0.1 mg/ml caffeine 0.2 mg/ml caffeine 0.3 mg/ml caffeine bpm bpm bpm % of BHR bpm % of BHR bpm % of BHR Heart 1 36 72 78 108.3 84 116.7 66 91.7 Heart 2 41 65 78 120.0 70 107.7 68 104.6 Heart 3 36 38 37 97.4 45 118.4 46 121.1       Group A tested the effects of the a wider range of caffeine concentrations, from 0.1mg/ml to 1.0 mg/ml (Table 2). As before, the heart beak faster when tehy were transferred from DMEM into 0.1 mg/ml caffeine. When the hearts were transferred into 0.5 mg/ml caffeine, the heart rates were lower than their base heart rates in DMEM. When the hearts were placed in an even higher concentration of caffeine, the 1.0 mg/ml caffeine solution, beating ceased. Table 2. The average heart rate in beats per minute (bpm) of four Group A heartse placed in DMEM, and in three caffeine solutions of concentrations 0.1mg/ml, 0.5 mg/ml and 1.0 mg/ml. The reaction of each heart to the various solutions is also shown as the percentage of the base heart rate (BHR) in DMEM. Group A Average # of bpm % of BHR DMEM (base rate) 32 100 0.1 mg/ml Caffeine 43 134.4 0.5 mg/ml Caffeine 19 59.4 1.0 mg/ml Caffeine 0 0.0 This experiment can also be conducted with intact embryos. Three- or four-day chick embryos were isolated and directly tested for an effect of caffeine on the heart rate. Table 3. Three day old chick embryos in Howards Ringer then treated with .25 mg/ml caffeine. Heart Beats per Minute Egg # Howard's Ringers Solution 0.25mg/ml Caffeine Difference In BPM 1 37 38 +1 2 40 43 +3 Table 4. Three day old chick embryos in Howards Ringer then treated ith .5 mg/ml caffeine. Heart Beats per Minute Egg # Howard's Ringers Solution 0.5 mg/ml caffeine Difference In BPM 3 30 38 +8 4 32 41 +9		Results Movies: Figures 2-6 (group A) Figure 7-10 (group B)

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