MOTOR CENTRES OF THE HEART. 99 



ability is diminished (e.g., by touching the septum with opium 

 Ludwig, Hoffa), other centres seem to undertake this function, in 

 which case the movement may extend from the ventricles to the 

 auricles. If a heart be cut into pieces, so that the individual pieces 

 still remain connected with each other, the regular peristaltic or 

 wave-like movements proceeding from the auricles to the ventricle, 

 may continue for a long time (Donders, Engelmann). If the heart, 

 however, be completely divided into two distinct pieces (auricle and 

 ventricle), the movements of both parts continue, but not in the same 

 sequence they beat at different rates. 



(3.) All stimuli of moderate strength applied directly to the heart 

 cause at first an increase of the rhythmical heart-beats ; stronger 

 stimuli cause a diminution, and it may be paralysis, which is often 

 preceded by a convulsive movement. Increased activity exhausts 

 the energy of the heart sooner. 



(4.) The auricular centres seem to be more excitable than those of 

 the ventricle; hence, in a heart left to itself the auricles pulsate 

 longest. 



(5.) The heart may be excited (reflexly) from its inner surface. 

 Weak stimuli applied to the inner surface of the heart greatly 

 accelerate the heart's action, the stimulus required being much 

 feebler than that applied to the external surface of the heart. 

 Strong stimuli, which bring the heart to rest, also act more easily when 

 applied to the inner surface than when they are applied to its outer 

 surface (Henry, 1832). The ventricle is always the part first to be 

 paralysed. 



(6.) In order that the heart may continue to contract, it is necessary 

 that it be supplied with a fluid which in addition to (Ludwig, Volk- 

 mann, Goltz) must contain the necessary nutritive materials. The most 

 perfect fluid, of course, is blood. Hence the heart ceases to beat 

 in an indifferent fluid (O'G p.c. sodium chloride), but its activity may 

 be revived by supplying it with a proper nutritive fluid. 



Cardiac Nutritive Fluids. These nutritive fluids are such as contain serum- 

 Lilbumin e.y., blood, serum, or lymph. Serum retains its nutritive properties 

 even after it has been subjected to diffusion (Martins and Kronecker). Milk and 

 whey (v. Ott), normal saline solution (O'G per cent. NaCl) mixed with blood, 

 albumin, or peptone, and 0'3 per cent, sodium carbonate (Kronecker, Merunowicz, 

 and Stienon), or a trace of caustic soda (Gaule), or a solution of the salts of 

 serum, are suitable. 



(7.) The independent pulsations of parts of the heart which are 

 devoid of ganglia, show that the presence of ganglia is not absolutely 

 necessary in order to have rhythmical pulsation. Direct stimulation 

 of the heart may cause these movements. But the ganglia are more 

 excitable than the heart-muscle itself, and they conduct the impulses 



