I'rucffJiiiys of tlw Ohio State Academy of Science 459 



eetitage of tlie L'X )2 in the blood stimulates the respiratory 

 centier in the medulla oblongata which will cause the muscle 

 .oi. .the cjiest to act more rapidly-, thereby eliminating more 

 CO^ and gaining more oxygen. We have already noticed that 

 the amount of blood going to an organ depends upon the 

 l)ressure of blood in that organ. The pressure of blood in 

 tlie organ depends largely upon the muscular activity in the 

 organ or in. -the surrounding tissues. A sudden closing of the 

 capillaries of the peripheral organs, wdiich would never occur 

 if the n^uscles were active, will natu-rally have a tendency to 

 throw the. blood to the iiiternal organs causing a congestion. 

 If tliere should' be any weakness in any one of them that organ 

 would suffer more tlian the otherg. , Many chronic diseases 

 are traced to this cause, for example, Hright's disease, dia- 

 betis. etc. 



The reason for many of the common rules to govern ex- 

 ercise can be' seen from the foregoing discussion, i. e. "We 

 should not, exercise vigorously on a full stomach." Exercise 

 reduces the pressure in the peripheral organs which will nat- 

 urallv take tlie blood away from, the. internal organs where it 

 is needed just at this time. Moderate exercise is not bad, for 

 the digestive organs are stimulated by the presence of food 

 whicii causes them to be active. The simple fact that they 

 are active in movement or in the secretion of digestive fluids 

 will cause less pressure in the organ and inore blood will set 

 in that direction in spite of a moderate call for blood in other 

 directions. The whole thing is relative and if the balance is 

 in favor of any organ that organ will get , the blood necessary 

 for it to do its work. 



A muscle does not tire so much from tlie work that it 

 does as from the impurities that it makes by its activity. In 

 case that products of metabolism are made faster than they 

 are carried off bv the circulation the body becomes tired in 

 proportion as the balance is in favor of the impurities. In 

 the case of extreme exercise the muscle tissue i,s actually brok- 

 en down faster than it can be built up, faster than food can be 



