ACTION OF FLUIDS ON THE HEART. 8 1 



strips still beat in a regularly progressive rhythmical manner, provided one strip 

 is caused to contract. The rapidity of the transmission is about 10 to 15 mm. per 

 sec. Hence, it appears that the conducting paths for the impulse causing the con- 

 traction are not nervous, but must be the contractile mass itself. It has not been 

 proved that nerve-fibres proceed from the ganglia to all the muscles. 



[According to Marchand's experiments, it takes a very long time for the excitement to pass 

 from the auricles to the ventricle a much longer time, in fact, than it would require to conduct 

 the excitement through muscle so that it is probable that the propagation of the impulse from 

 the auricles to the ventricle is conducted by nervous channels to the auriculo-ventricular 

 nervous apparatus. In fact, in the mammalian heart the muscular fibres of the auricles are 

 quite distinct from those of the ventricles.] 



(4) When the apex of a frog's heart is ligatured off from the rest of the heart, it 

 no longer pulsates {Reidenhain, Goltz), but such an apex, if stimulated directly, 

 e.g., by a prick of a pin, responds with a single contraction. If the " heart-apex " 

 be filled with normal saline solution under pressure, which acts as a stimulus, the 

 heart begins to pulsate, and the same is the case with a solution of delphinin or 

 quinine. If a cannula be tied into the heart over the auriculo-ventricular groove, 

 the ventricle does not beat, but if the ventricle be filled through the cannula with 

 blood containing oxygen, under a constant and sufficient pressure, it also pulsates 

 (Ludwig and Merunowicz). 



[(5) Luciani found that a heart ligatured above the auriculo-ventricular groove, 

 when filled with pure serum, produced groups of pulsations with a long diastolic 

 pause between every two groups (fig. 59). The successive beats in each group 



Fig. 59. 



Four groups of pulsations with intervening pauses, with their " staircase " character. The 



points on the abscissa were marked every 10 seconds. 



assume a "staircase" character (p. 84). These periodic groups undergo many 

 changes j they occur when the heart is filled with pure serum free from blood- 

 corpuscles, and they disappear and give place to regular pulsations when defibrinated 

 blood or serum containing haemoglobin or normal saline solution is used (Bossbach). 

 They also occur when the blood within the heart has become dark-coloured, i.e., 

 when it has been deprived of certain of its constituents, and if a trace of veratrin 

 be added to bright red blood they occur.] 



(6) An apex preparation, when stimulated with even a weak induction shock, 

 always gives its maximal contraction, and when a tetanising current is applied, 

 tetanus does not occur (Kronecker and Stirling). When the opening and closing 

 shocks of a sufficiently strong constant current are applied to the heart-apex, it 

 contracts with each closing or opening shock. [When a constant current is applied 

 to the lower two-thirds of the ventricle (heart-apex), under certain conditions the 

 apex contracts rhythmically. This is an important fact in connection with any 

 theory of the cardiac beat.] 



(7) If the bulbus aortse (frog) be ligatured, it still pulsates, provided the internal 

 pressure be moderate. Should it cease to beat, a single stimulus makes it respond 

 by a series of contractions. Increase of temperature to 35 C, and raising the 

 pressure within it, increase the number of pulsations (Engelmann). 



Action of Fluids. Haller was of opinion that the venous blood was the natural 

 stimulus which caused the heart to contract. That this is not so, is proved at once 



F v 



