124 SPECIAL ANATOMY. 



upon the capillary vessels ramifying throughout, but upon a peculiarity in the 

 colouring matter united with them. The fibres are soft, but firm, and during 

 life with difficulty torn ; their elasticity is trifling. After death they become 

 stiff (from seven to ten minutes), as the fibrin coagulates, which is the rigid- 

 ity of death, rigor mortis. 



3. Physiological Characters. Muscles are endowed with the faculty of 

 contracting in the direction of their fibres. In consequence, those parts be- 

 tween which they are attached approach more closely together. The con- 

 traction, by means of which the fibres shorten, become closer and harder, oc- 

 curs in consequence of the sudden bending together of the fibres, from the 

 extremities towards the centre, or curling up in a zigzag form, in the trans- 

 verse striae (crispalio), and is the result of an influence, which the will, the 

 blood, and certain external irritations, exercise upon the numerous interlaced 

 (motor) nerve fibres in the muscles. The irritability (irritabilitas HalkrT) of 

 the muscles (produced by gal vanism, cold, &c.) is only extinct some time after 

 death. Also, the slight shortening maintained during life (tension, tonus") ter 

 minates immediately with death, or by palsy of the nerves. Whilst at rest 

 the muscles possess their greatest power (Schwann). During every con- 

 tinued movement a small quantity of Plasma is effused which, becoming meta- 

 morphosed into the substance of the muscle, accounts for their increase of 

 size. Muscles act (generally) as the power in levers of the third order, that 

 is to a disadvantage, since the power is broken between the fulcrum and the 

 weight. 



144. c. Vessels and nerves of muscles. 



Arteries. They generally enter on the inner side of the middle part of the 

 muscle, dividing between the larger bundles into large branches, from which 

 smaller pass off between the smaller bundles, until they finally go into a long 

 capillary network which encompasses the primitive fibres, and discharges into 

 the veins which follow the course of the arteries. 



Nerves correspond in number and size (riot always) to that of the muscles. 

 The nerves of motion principally prevail over those of sensation, in muscles, 

 with which their trifling degree of sensation corresponds. They generally 

 enter the muscle at the posterior part of the superior fourth, take a course 

 like the arteries, but form loops at the ends, from which delicate filaments 

 pass off and encompass the primary bundles of fibres. 



145. d. Classification of muscles. 



In each muscle we may distinguish the fleshy central portion 

 (belly) ; the origin, the fixed point, head ; the insertion, the mov- 

 ing point, tail. Both the last are provided with tendinous fibres. 



1. According to the structure we distinguish animal and organic muscles. 

 (See before.) 



a. The animal muscles are striated, generally dark red, attached especially 

 to bones, and lie on the external boundary of the body ; they are connected 

 by tendons, and have antagonist muscles; they are generally thick, cylindrical, 

 sometimes even expanded like a membrane ; lastly, they are stimulated to 

 motion by the will. To this class belong the muscles of the trunk [arid ex- 

 tremities] and of the commencement of internal canals. 



#. The inorganic muscles are unstriped, generally pale red, lie in the inte- 



