86 PHYSIOLOGY OF MUSCLES AND NERVES. 



passes rapidly into the blood, and is, therefore, espe- 

 cially capable of rapidly replacing the expended forces. 

 It is not suitable for a sole or main food material durino- 

 long periods, because when a great quantity of sugar 

 is introduced into the stomach it is transformed into 

 lactic acid 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- 

 perature 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 0° 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, 45°, the 

 contractile power is lost in a few minutes. Exactly 

 the same happens in muscles yet remaining within the 

 body of the animal if the blood-current ceases to pass 

 through the body, either because of the death of the 

 animal, or in consequence of the local application of 

 ligatures to the vessels. This loss of contractile power 

 is spoken of as the death of the muscle. Muscular 

 death does not, therefore, correspond in time with the 

 general death of the whole animal, but it follows this 



