60 NAlUiiAL THEOLOaY. 



chamcal hi the animal frame, and what is. The nervoujs 

 influence — for we are often obliged to give names to things 

 which we know little about — I say, the nervous influence, 

 by which the belly or middle of the muscle is swelled, is not 

 mechanical. The utility of the effect we perceive — the 

 means, or the preparation of means, by which it is produced, 

 we do not. But obscurity as to the origin of muscular mo- 

 tion brings no doubtfulness into our observations upon the 

 sequel of the process ; w^hich observations relate, first, to the 

 constitution of the muscle, in consequence of which consti- 

 tution, the swelling of the belly or middle part is necessarily 

 and mechanically followed by a contraction of the tendons , 

 secondly, to the number and variety of the muscles, and the 

 corresponding number and variety of useful powers which 

 they supply to the animal, which is astonishingly great ; 

 thirdly, to the judicious — if we may be permitted to use that 

 term in speaking of the Author, or of the works of nature — 

 to the wise and well-contrived disposition of each muscle for 

 its specific purpose — for moving the joint this way, and that 

 way, and the other way — for pulling and drav/ing the part 

 to which it is attached in a determinate and particular di- 

 rection, which is a mechanical operation, exemplified in s 

 multitude of instances. To mention only one : the tendon 

 of the trochlear muscle of the eye,^ to the end that it may 

 draw in the line required, is passed through a cartilaginous 

 ring, at which it is reverted exactly in the same manner as 

 a rope in a ship is carried over a block, or round a stay, in 

 order to make it pull in the direction which is wanted. All 

 this, as we have said, is mechanical, and is as accessible to 



* Plate II., Fig. 1. The trochlear or superior oblique muscle 

 arises with, the straight muscles from the bottom of the orbit. Its 

 muscular portion, a, is extended over the upper part of the eyeball, 

 and gradually assumes the form of a smooth round tendon, 6; this 

 passes through the pulley, c, which is fixed to the inner edge of the 

 orbit, cf, then returning backwards and downwards, c, is inserted into 

 the sclerotic membrane, f. The use of this muscle is to bring the eye 

 forwards, and turn the pupil downwards and outwards. 



