CIRCULATION. 151 



current. 1 Very strong currents cause tonic contraction. An apex made inac- 

 tive by Bernstein's crushing can be made to beat again by clamping the aorta 

 and thus raising the endocardiac pressure. Chemical stimulation is also effec- 

 tive. Delphinin, quinine, muscarin with atropin, atropin alone, morphin 

 and various other alkaloids, dilute mineral acids, dilute alkalies, bile, sodium 

 chloride, alcohol, and other bodies, 2 when painted on the resting ventricle, call 

 forth a longer or shorter series of beats. Stimulation with induction shocks 

 gives a similar result. 



Other muscles in which no nerve-cells have been discovered can contract 

 rhythmically. Thus the bulbus aortse of the frog beats regularly after its 

 removal from the body, even the smallest pieces showing under the microscope 

 rhythmical contractions. Engelmann, who observed this fact, declares that 

 the entire bulbus is lacking in nerve-cells. This is contradicted by Dogiel ; 

 yet it seems hardly reasonable that these " smallest pieces " which Engelmann 

 mentions were each provided with ganglion-cells. It is more probable that the 

 contractions were the result of a constant artificial stimulus. Curarized stri- 

 ated muscles placed in certain saline solutions may contract from time to time. 

 The hearts of many invertebrates in which ganglion-cells are apparently absent 

 beat rhythmically. 



Much has been made of the fact that the ganglion-cells grow into the heart 

 long after the cardiac rhythm is established, showing that the embryonic heart 

 muscle has rhythmic contractile powers. The adult heart muscle, it is alleged, 

 retains certain embryonic peculiarities of structure, and as structure and func- 

 tion are correlated, should also retain the embryonic power of contraction 

 without nerve-cells. 



A positive demonstration that the nerve-cells in the heart are not essential 

 to its contractions is secured by removing the tip of the ventricle of the dog's 

 heart and supplying it with warm defibrinated blood through a cannula tied 

 into its nutrient artery. Long-continued, rhythmical, spontaneous contrac- 

 tions are thus obtained. 3 As the part removed contains no nerve-cells, the 

 observed contractions can only arise in the muscular tissue, provided we make 

 the (at present) safe assumption that the nerve-fibres d<> not originate im- 

 pulses capable of inducing rhythmic muscular contractions. The demonstra- 

 tion that the nerve-cells are not essential to contraction, places us one step 

 nearer the true cause of contraction. It is some agency acting on the con- 

 tractile substance. Evidence is accumulating that this agent is a chemical 

 substance, or substances, brought to the contractile matter by the blood. 

 For this chemical stimulation calcium is apparently essential, and for rhythmic 

 contraction and relaxation Howell 4 finds a certain proportion of potassium 



1 Langendorff: Archivfur die gesammte Physiologic, L895, Ixi. p. 33(5. 



2 Kaiser: Zeitschnfi fur Biologic, L895, xxxii. p. (>. 



3 Porter: Journal of Experimental Medicine, 1X97, ii. p. 391. 



* Howell : American Journal of Physiology, 1898, ii. p. 17; Loeb: Ibid., 1900, iii. p. 394. 

 The reader is recommended to examine these BUggestive papers for himself. 



