8(5 rilYSIUl.oiiY OF MUSCLES AND NERVES. 



pusses rapidly into the blond, and is, therefore, espe- 

 cially capable of rapidly replacing the expended forces. 

 Ii i> not suit, ill].' for ;i sole or main food material duriii"- 



& 



long periods, because when, a great quantity of sugar 

 i- introduced into tin- stoiuaeli it is transformed into 

 laetie arid and the digestion is injured. 



5. When muscles have lain by for some time after 

 their extraction from the body, a change occurs in them 

 which deprives them of their capacity for contracting 

 when irritated. This change intervenes yet more 

 rapidly when they are induced to pass into a state of 

 activity by many repeated irritations. The time neces- 

 sary for the intervention of this change varies much, 

 and depends chiefly on the nature of the animal and on 

 the temperature. The muscles of mammals in a tem- 

 pi -rature such as that of an ordinary room lose their 

 power of contraction in as little as from twenty to 

 thirty minutes; the muscles of frogs do not lose this 

 power for several hours, and some from the calf-muscle of 

 a frog have been observed to pulsate even for forty-eight 

 hours in the temperature of an ordinary room. At a 

 temperature of from to 1 C. the same muscle may 

 retain its power of contraction even for eight days. On 

 the other hand, in a temperature of, or above, -4,1 . the 

 contractile power is lo.-t in a Jew minutes. Kxact ly 

 the same happen.- in mu.-eles yet remaining within the 

 liodv f the animal if the blood-current ceases to pa>s 

 through the body, either because of the death of the 

 animal, or in e<Mi><-i|uence of the local application of 

 ligatures to the vessels. This loss of contractile po\\er 

 is spoken of as the <//(//// of the muscle. ^Muscular 

 death does not, therefore, correspond j n time with the 

 general death of the \\ hole animal, but it follows this 



