Mr. Carlisle’s Lecture 
and, from the improved state of collateral branches of know- 
ledge, together with the addition of new sources, and methods 
of investigation, it may not be unreasonable to hope for an 
ultimate solution of these phenomena, no less complete, 
and consistent, than that of any other desideratum in physical 
science. 
The present attempt to forward such designs is limited to 
circumstances which are connected with muscular motion, con- 
sidered as causes, or rather as a series of events, all of which 
contribute, more or less, as conveniences, or essential requi- 
sites, to the phenomena ; the details of muscular applications 
being distinct from the objects of this lecture. 
No satisfactory explanation has yet been given of the state 
or changes which obtain in muscles during their contractions 
or relaxations, neither are their corresponding connections 
with the vascular, respiratory, and nervous systems, sufficiently 
traced. These subjects are therefore open for the present en- 
quiry, and although I may totally fail in this attempt to elu- 
cidate any one of the subjects proposed, nevertheless I shall 
not esteem my labour useless, or the time of the Royal Society 
altogether unprofitably consumed, if I succeed in pointing out 
the way to the future attainment of knowledge so deeply 
interesting to mankind. 
The muscular parts of animals are most frequently com- 
posed of many substances, in addition to those which are purely 
muscular. In this gross state, they constitute a flexible, com- 
pressible solid, whose texture is generally fibrous, the fibres 
being compacted into fasciculi, or bundles of various thickness. 
These fibres are elastic during the contracted state of muscles 
after death, being capable of extension to more than one-fifth 
