Royal Institution, 71 



ROYAL INSTITUTION OF GREAT BRITAIN. 



Friday, May 15, 1857. — The Lord Wensleydale, Vice-President, 

 in the (^hair. 



** On the present state of Knowledge as to the Structure and 

 Functions of Nerve." By Thomas H. Huxley, F.R.S., Fullerian 

 Professor of Physiology, Royal Institution. 



The speaker commenced by directing the attention of the audience 

 to an index, connected with a little apparatus upon the table, and 

 vibrating backwards and forwards with great regularity. The cause 

 of this motion was the heart of a frog (deprived of sensation, though 

 not of life) which had been carefully exposed by opening the peri- 

 cardium, and into whose apex the point of a needle connected with 

 the index had been thrust. Under these circumstances the heart 

 would .go on beating, with perfect regularity and full force, for hours; 

 and as every pulsation caused the index to travel through a certain 

 arc, the effect of any influences brought to bear upon the heart could 

 be made perfectly obvious to every one present. 



The frog's heart is a great hollow mass of muscle, consisting of 

 three chambers, a ventricle and two auricles, the latter being separated 

 from one another by a partition or septum. By the successive con- 

 traction of these chambers, the blood is propelled in a certain direc- 

 tion ; the auricles contracting, force the blood into the ventricle ; 

 the ventricle then contracting, drives the blood into the aortic bulb ; 

 and it is essential to the full efficiency of the heart as a circulatory 

 organ, that all the muscular fibres of the auricles should contract 

 together, and that all the muscular fibres of the ventricle should 

 contract together ; but that the latter should follow the former action 

 after a certain interval. 



The contractions of the muscles of the heart thus occur in a defi- 

 nite order, and exhibit a combination towards a certain end. They 

 are rhythmical and purposive ; and it becomes a question of extreme 

 interest to ascertain, where lies the regulative power which governs 

 their rhythm. 



If we examine into the various structures of which the heart is 

 composed, we find that the bulk of the organ is made up of striped 

 muscular fibres, bound together as it were by connective tissue, and 

 coated internally and externally with epithelium. Now it is certain 

 that the regulative power is not to be found in any of these tissues. 

 The two latter may, for the present purpose, be regarded as unim- 

 portant, as they certainly take no share either in producing or 

 guiding the movements of the heart. The muscular tissue, on the 

 other hand, though the seat of the contractility of the organ, requires 

 some influence from without, some stimulus, in order to contract at 

 all, and having once contracted, it remains still until another stimulus 

 excites it. There is, therefore, nothing in its muscular substance 

 which can account for the constantly recurring rhythmical pulsations 

 of the heart. 



Experiments have been made, however, which clearly show that 



