-S02 PHYSIOLOGY FOR DENTAL STUDENTS. 



The Chemical Changes Which Accompany Muscular Contrac- 

 tion are concerned in the liberation of energy by the oxidation 

 of the organic foodstuffs and the converting of this energy into 

 muscular energy. Just how this change is brought about is not 

 known. During muscular activity a great amount of oxygen is 

 required and a large amount of carbon dioxide is given off. It 

 is very interesting, however, to know that the maximal exchange 

 of these gases does not actually accompany, but follows the mus- 

 cular activity, thus indicating that a muscle becomes charged 

 with energy, so to speak, during rest and discharges itself in 

 much the same manner as a storage battery during a period of 

 activity. If a muscle be made to contract till it becomes fatigued, 

 a large amount of sarco-lactic acid accumulates in the tissue. This 

 poisons the muscle and makes it unable to contract. If this be 

 washed out with saline, the muscle will again contract for a time. 

 Rigor mortis, or the rigidity which comes on after death, in.iy 

 be due to the development of sarco-lactic acid in the tissues be- 

 cause they have become deprived of oxygen. 



