

MUSCULAR FIBRE. 197 



the forms presented by the latter, being in the Fibrous tissues, which, 

 as already observed, are introduced for the sake of facilitating the 

 movements of the several parts of the structure, one upon the other. 

 The various cellular tissues find their exact representatives in those of 

 the Vegetable fabric; and the denser parts of the Animal, such as 

 Bone, Cartilage, &c., are represented by the solid substances formed 

 by the Plant in the heart-wood of the stem, the stone of fruits, &c., 

 these substances acquiring their density in precisely the same manner 

 with the Osseous tissues, by the secreting- action of their own cells, 

 which draw a solidifying material from the general circulating fluid. 

 But we now come to two tissues of the highest importance in the Animal 

 fabric, the presence of which is, indeed, its distinguishing characteristic. 

 These are the Muscular and the Nervous tissues. The former is the 

 one by which all the sensible movements of the body are effected ; and 

 the latter furnishes the instrument by which sensations are received, 

 and by which the will excites the muscles to action, besides serving as 

 the medium for other operations, in which motion is produced without 

 the intervention of either sensation or will. These tissues, with the 

 apparatus of bones and joints on which the muscles act, constitute the 

 purely animal portion of the fabric ; and if a being could be constructed, 

 in which they should be capable of continued activity without any other 

 assistance, it would be in all essential particulars an Animal. But, as 

 we shall presently see, the plans on which these tissues are formed, in 

 fact, the very conditions of their existence and activity, are such, that 

 they require constant nutrition and re-formation ; so that the Animal 

 cannot exist without an apparatus for preparing, circulating, and main- 

 taining in constant purity, a fluid by which nutrient operations may be 

 effected, and which shall also be the means of carrying off the products 

 of the waste consequent upon the action of those tissues. This appa- 

 ratus constitutes the Vegetative portion of the frame, the elementary 

 parts concerned in which have been already noticed. 



332. When we examine an ordinary Muscle with the naked eye, we 

 observe that it is made up of a number of fasciculi or bundles of fibres ; 

 which are arranged side by side with great regularity, in the direction 

 in which the muscle is to act, and which are united by areolar tissue. 

 These fasciculi may be separated into smaller parts, which appear like 

 simple fibres ; but when these are examined by the microscope, they 

 are found to be themselves fasciculi, composed of minuter fibres bound 

 together by delicate filaments of areolar tissue.; By carefully sepa- 

 rating these, we may obtain the ultimate Muscular Fibre. This fibre 

 exists under two forms, the striated and the non-striated; the former 

 makes up the whole substance of those muscles over which the will has 

 control, or which are usually called into operation through the nerves ; 

 whilst the latter exists in the muscles which the will cannot influence, 

 and which are excited to contraction by stimuli that act directly upon 

 them. The muscles of the former class minister especially to the animal 

 functions ; those of the latter to the functions of organic or vegetative 

 life. The appearance presented by the striated fibres of ordinary 

 muscles is shown in Fig. 58; that of the non-striated fibres of the 

 muscles of organic life, in Fig. 59. 



