66 PBINCIPLES OF "VETEBINAKY SCIENCE 



observed in the muscles after death. It is caused by a shortening 

 of the muscles as a result of postmortem changes and brings about 

 movements in the carcass that resemble those of life. When it 

 occurs in the corpse of a man watchers at the bier are often 

 horrified. 



A summary of the chemical changes normally taking place in 

 living muscles follows : 



1. The oxygen, which is brought to the muscles from the lungs, 

 is used for the combustion of the carbohydrates, proteins, and 

 fats brought from the intestines. 



2. The stored glycogen is converted into glucose. 



3. The products of these chemical changes are carbon dioxide, 

 water, sarcolactic acid, and energy. 



4. The energy produced is in the form of heat and work. 



In the absence of food, muscles produce heat and perform work 

 at the expense of their stored-up carbohydrates. Except in 

 starvation, the proteins do not furnish energy as there is no 

 provision for their storage. 



The physiologic properties of involuntary muscles differ in 

 some respects from those of the voluntary group. The chief 

 differences are their power to remain contracted for a long period 

 and their great rhythm and force of movement. Response to 

 stimuli is from one hundred to five hundred times slower, but 

 it occurs with greater regularity, is more marked, and lasts 

 longer. This is seen by pinching the exposed intestine or rubbing 

 the hand over the stomach wall, when peristaltic movements 

 immediately set in. 



Heart muscle contracts slower than voluntary but faster than 

 other visceral muscles. Its property of rhythmic contractility 

 is developed to a wonderful degree. When the heart contracts 

 at all it does so to its utmost ability. Other functions of heart 

 muscle will be taken up when the circulation of the blood is 

 studied. 



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