6 
Mr. Carlisle's Lecture 
The muscles of birds are not different, in any respect, from 
those of quadrupeds of the class of mammalia. 
The anatomical structure of muscular fibres is generally 
complex, as those fibres are connected with membrane, blood- 
vessels, nerves, and lymphasducts ; which seem to be only 
appendages of convenience to the essential matter of muscle. 
A muscular fibre, duly prepared by washing away the ad- 
hering extraneous substances, and exposed to view in a powerful 
microscope, is undoubtedly a solid cylinder, the covering of 
which is reticular membrane, and the contained part a pulpy 
substance irregularly granulated, and of little cohesive power 
when dead. 
A difficulty has often subsisted among anatomists concerning 
the ultimate fibres of muscles ; and, because of their tenuity, 
some persons have considered them infinitely divisible, a 
position which may be contradicted at any time, by an hour's 
labour at the microscope. 
The arteries arboresce copiously upon the reticular coat of 
the muscular fibre, and in warm-blooded animals these vessels 
are of sufficient capacity to admit the red particles of blood, 
but the intrinsic matter of muscle, contained within the ultimate 
cylinder, has no red particles. 
The arteries of muscles anastomose with corresponding 
veins ; but this course of a continuous canal cannot be sup- 
posed to act in a direct manner upon the matter of muscle. 
The capillary arteries terminating in the muscular fibre 
must alone effect all the changes of increase in the bulk, or 
number, of fibres, in the replenishment of exhausted materials, 
and in the repair of injuries ; some of these necessities may be 
supposed to be continually operating. It is well known, that 
