412 Prof. Th. W. Engelmann. [Mar. 14, 



the founders of our present doctrine of muscular structure and 

 action a man whose name will live on, in my home in Holland, of all 

 countries, associated with the memory of his great brotherly friend, 

 Ponders, and whom, to my great grief, I may see here no more I 

 mean Sir William Bowman. 



But a few years ago I had the happiness of seeing him in Utrecht, 

 and of observing how the interest which he took in a province of 

 science in which he had gained his first laurels remained unchanged, 

 even after the lapse of half a century. To behold him among this 

 audience would have been my greatest joy and pride, and his judgment 

 would, in my eyes, have been invaluable. May that which I am now 

 going to say be commended to you at the same time as homage paid 

 to the memory of the discoverer of the sarcous elements and of the 

 waves of contraction. 



The subject of my lecture is an inquiry into " The Nature of 

 Muscular Contraction," Like all vital phenomena, muscular con- 

 traction is a most complicated process, composed of . mechanical, 

 chemical, thermal, and electrical changes in living matter. Hence 

 it will be our task to become acquainted with these changes as com- 

 pletely and exactly as possible, and to ascertain their causal con- 

 nection. Our inquiry must not be restricted to one special kind of 

 muscle : it will have to extend to all the different forms, the highest 

 as well as the lowest muscles in every stage of development, muscles 

 either sound or unsound, for there can be no doubt but that in all 

 these cases the principle of activity is the same. Nay, it will be necessary 

 to deal even with the other phenomena of so-called contractility, such 

 as protoplasmic and ciliary motion, for all those different types of 

 organic movement, however much they may differ from each other in 

 details, are yet connected by states of gradual transition, so that, to 

 all appearance, one principle of motion, essentially the same, is 

 applicable to all of them. 



Only such properties and processes as all contractile structures 

 have in common will consequently have a right to be considered 

 essential to the process of contraction, and only such will be allowed 

 to form the basis of our endeavours to explain muscular motion. 



The general mechanical principle on which muscular contraction 

 is based, will apparently be discovered when we shall have ascer- 

 tained in what way the power of shortening proceeds from the 

 potential chemical energy which disappears upon stimulation of the 

 muscle. There can be no doubt as to the fact, that the potential 

 chemical energy of the component parts of muscular substance is 

 alone the ultimate source of this power, for the existence of any other 

 source cannot be proved. 



The quantity of energy which is imparted to the muscle by the 



