880 



ANNUAL REGISTER, 1804. 



lique muscles attached to the head 

 are likewise so disposed, as to be 

 capable of steadying the globe, as 

 well as of moring it. The head of a 

 new born infant is often obliged to 

 be fillctted up. Afterwards the head 

 drops, and rolls in every direflion. 

 So that it is by the equilibre of the 

 muscles, by the aid of a considerable 

 and equipollent muscular force in 

 constant exertion, that the head 

 maintains its ereft posture. The 

 muscles here supply what would 

 otheni^'se be a great defeat in the 

 articulation; for the joint in the 

 neck, although admirajjly adapted 

 to the motion of the head, is insuf- 

 ficient for its support. It is not 

 only by the means of a most curious 

 strudture of the bones that a man 

 turns his head, but by virtue of an 

 adjusted muscular power, that he 

 even holds it up. 



As another example of what we 

 are illustrating, viz. conformity of 

 use between the bones and the mus- 

 cles, it has been observed of the 

 difterent vertebrae, that their pro- 

 cesses are exactly proporiioncd to 

 the quantity of motion which the 

 other bones allow of, and which the 

 respective muscles arc capable of 

 producing. 



2. A muscle acts only by cort- 

 tra6tion. Its force is exerted in no 

 other way. When the exertion 

 ceases, it relaxes itself ; that is, it 

 returns by relaxation to its former 

 state, but without energy. This is 

 the nature of the muscular fibre ; 

 and being so, it is evident that the 

 reciprocal energetic motion of the 

 limbs, by which we mean motion 

 with force in opposite dircftions, 

 can only be produced by the instru- 

 mentality of opposite or antagonist 

 muscles; of flexors and extensors 

 answering to each other. I'or in- 



stance, the biceps and hi'acliioeus in- 

 (emus muscles placed in the front 

 part of the upper arm, by their con- 

 traction bend the elbow ; and with 

 such degree of force, as the case re- 

 quires, or the strength admits of. 

 The relaxation of the muscles after 

 tlie effort, would merely let the 

 fore-arm drop down. For the 

 back stroke, therefore, and that 

 the arm may not only bend at the 

 elbow, but also extend and straight 

 itself with force, other muscles, the 

 longifs and brcvisbrachiccuscxternusy 

 and the anconcceus placed on the 

 hinder part of the arm, by their 

 conlractile twjtch, fetch back the 

 fore-arm into a straight line with the 

 cubit, with no less force than that 

 with which it Mas bent out of it. 

 The same thing obtains in all the 

 limbs, and in every moveable part 

 of the body. A finger is not bent 

 and straightened Avithout the con- 

 tra6lion of two muscles taking 

 place. It is evident, therefore, that 

 the animal funi^ions require that 

 particular disposition of the mus- 

 cles which we describe by the name 

 of antagonist muscles ; and they 

 are accordingly so disposed. Every 

 muscle is provided with an adver- 

 sary. They act like two sawyers in 

 a pit, by an opposite pull ; and no- 

 thing surely can more strongly indi- 

 cate design and attention to an end 

 than their being thus stationed; than 

 this collocation. The nature of the 

 muscular fibre being Mhat it is, the 

 purposes of the animal could be an- 

 swered by no other. And not only 

 the capacity for motion, but the 

 aspect and symmetry of the body, 

 is preserved by the muscles being 

 marshalled according to this order, 

 e. g. the mouth is held in the mid- 

 dle of the face, and its angles kept 

 in a state of exact correspondency, 



by 



