282 Br W. H. Gaskett, On certain points [Nov. 27, 



tissue of the auricle of the tortoise can be taught to beat rhyth- 

 mically. 



/ conclude, then, that every part cf the muscular tissue of the 

 tortoise heart possesses the property of spontaneous rhythmical 

 contraction, and that the difference in function between the 

 muscular tissue of one part and that of another depends upon 

 the extent to luhich that property has become on the one li<in<l 

 specially developed or on the other hand rudimentary, owing to 

 the greater development of some other property such as rapidity 

 of contraction, luhich was more advantageous for the efficiency 

 of the heart as a whole. 



In the muscular tissue of the frog's ventricle this rhythmical 

 property seems to be still more rudimentary than in the tortoise ; 

 I have not yet succeeded in teaching a strip from the apex of 

 the frog's ventricle to beat spontaneously, though the experiments 

 of Merunowicz and others are sufficient to show how little extra 

 assistance is needed to bring about the required condition of the 

 muscle. 



In conclusion, I will put the question : Is not the power of 

 spontaneous rhythmical contraction a fundamental property of 

 all contractile tissue, a property which has in some cases de- 

 veloped so as to become the chief attribute of the muscle in 

 question, in other cases has fallen more or less into the back- 

 ground, become more or less rudimentary according as the muscle 

 has specialized in other directions, such as the power of rapid 

 contraction, tonic contraction, etc. ? To discuss this question 

 at full length would take up too much time, I will only say that 

 recent investigations have shown that in all three kinds of mus- 

 cular tissue unstriped, cardiac, and striped (especially in more 

 lowly developed animals), it is possible in different ways, apart 

 from rhythmical stimulation, to throw the tissue into such a 

 condition that rhythmical contractions result, even when no signs 

 of ganglion cells are to be found. 



Part II. — Onthe action of a weak interrupted current upon certain 

 functions of the cardiac muscle, and its resemblance to the 

 action of the vagus nerve. 



In my first paper 1 on the action of the vagus nerve, I have 

 shown that stimulation of the vagus in the frog produces through- 

 out pairs of opposite effects which are not dependent on each other, 

 but may each one occur separately. Thus we may have 



1. Slowing and acceleration of rhythm, 



2. Diminution and increase of the force of the contractions, 



3. Diminution and possibly increase of tone. 



1 Phil. Trans. 1882. 



