128 



THE CAT. 



Shortly after death a peculiar rigidity of the muscles sooner or 

 later sets in,which may be so intense that rupture of tissue will take 

 place rather than change of rjosture, if force be applied to produce the 

 latter. This is the death-stiffening, or rigor mortis. 



This rigidity does not alter the position in which the limbs may 

 happen to be when it sets in.* It appears to be due to a solidifica- 

 tion (coagulation) of the fluid substance of the muscular tissue. 



The occurrence of rigor mortis is a certain proof that death has 

 taken place. 



4. Muscular fibres being thus aggregated, as has been said, 

 into various masses termed muscles, the number of these masses 

 may be estimated at some 500 in the cat. They vary greatly in 

 size, in weight, in form and in the arrangement of their fasciculi. 

 Generally, the fasciculi are arranged longitudinally in a more or less 

 parallel manner, and end by insertion side by side into a tendon ; 

 but sometimes they radiate from a central band of dense fibrous 

 tissue (or tendon) in a penniform or semi-penniform manner. Some- 

 times they are arranged in a concentric manner round apertures, 

 when they are called sphincters ; or in a cylindrical manner, as in 

 the walls of the alimentary canal. They may have, as in the last 

 named instance, no connexion with bone, but generally they are 

 attached to bones which they employ (as we shall shortly see) as 

 levers or fulcra, and are then generally inserted by means of those 

 dense bands of parallel fibres of connective tissue called tendons. 



The fleshy mass of a muscle is called the belly, and there may be 

 two such bellies with an intermediate tendon. Such a muscle is 

 termed digastric. A muscle may arise by two or more heads, when 

 it is called bi~ or tri-tipital, as the case may be. 



That end of a muscle which is nearest to the central axis of the 

 whole body, or to the root, or axis of the limb of which it forms 

 part, is generally called its ORIGIN, or its " proximal end." The 

 opposite extremity is generally called its INSERTION, or its " distal 

 end." 



Muscles acting on bony levers produce definite motions of different 

 kinds, according to the circumstances of their application. This 

 difference of functions causes them to be distinguished by certain 

 generic terms, each such term being applied to all such muscles as 

 produce a motion of the kind denoted by the term. 



Thus, muscles which bend a joint so as to make the angle formed 

 by two long bones acute, or which move the digits towards the 

 palmar or plantar surfaces of the feet, are termed FLEXORS. Those 

 the function of which is antagonistic to these are termed EXTENSORS. 



Some muscles attached to a long bone which is relatively fixed at 

 one end, tend to make it describe the superficies of a cone, or a 

 movement of circumduction. Such muscles are termed ROTATORS. 



* Occasionally after death, from cholera 

 and yellow fever, distinct movements 

 have been observed in the human sub- 



ject ; but these are probably due to some 

 action of decomposition on parts of the 

 nervous system. 



