(_b_) _NaCl_ + _CaCl_{2}_. The phenomena described above as occurring when isolated loops of intestine are immersed in mixtures of LiCl and CaCl_{2} can be produced also in mixtures of NaCl and CaCl_{2}. The behavior of loops placed in pure CaCl_{2} and in pure NaCl has been described. In the former the loop remains motionless; in the latter regular rhythmical movements continue for 40 minutes or more. When, however, a loop is placed in 50 c.c. m/6 NaCl + 10 c.c. m/6 CaCl_{2} there are no movements whatever to be seen at first. The loops remains quiet for about 10 minutes. The movements which are seen from the beginning in the control loop in pure NaCl solution have apparently been inhibited by the CaCl_{2} present in the mixture. After 10 minutes, however, the loop gradually becomes very active, and violent contractions appear which are similar to those described as taking place in mixtures of LiCl and CaCl_{2}. The loop becomes much more active than the control loop in pure NaCl. The onset in the LiCl mixture is more sudden, but otherwise the phenomenon is practically the same. The movements in NaCl + CaCl_{2} persist for 30 or 40 minutes, sometimes for an hour. When the concentration of the CaCl_{2} in the mixture is relatively great this effect is not obtained. This is shown in the following table:-- Time 50 c.c. NaCl 50 c.c. NaCl 50 c.c. NaCl + 5 c.c. CaCl_{2} + 10 c.c. CaCl_{2} 10:35 quite active no movements no movements 10:40 quite active no movements no movements 10:45 quite active slight movements slight movements 10:50 less active slight movements slight movements 10:55 still active very active very active 11:00 still active extremely active extremely active 11:15 still active extremely active extremely active 11:30 almost stopped extremely active extremely active 11:45 no movements movements quieter movements quieter 11:50 no movements no movements no movements Time 50 c.c. NaCl 50 c.c. NaCl 50 c.c. CaCl_{2} + 20 c.c. CaCl_{2} + 40 c.c. CaCl_{2}