RESPIRATION. 99 



the lymph that surrounds them ; that while the lymph is 

 continually fed by the blood, there is not a great pressure 

 given in this way. The lymph stream is largely depend- 

 ent on the pressure of the surrounding organs. When 

 one takes a good deal of muscular exercise the lymph is 

 renewed with rapidity enough to supply the tissues with 

 food, and to carry away their wastes. But in those who 

 sit quiet a large share of the day, taking no more exercise 

 than is necessary to take them to and from their places 

 of business, the lymph becomes too nearly stagnant, the 

 tissues are not well nourished, and the whole body suffers. 



Deep Breathing. It is a grateful relief to the whole 

 system to stand, stretch, inhale deeply and slowly several 

 times, and to repeat this every hour or so. Every one en- 

 gaged in office work or studying should form this habit, 

 especially if he does not give an hour daily to exercise in 

 a gymnasium, or otherwise. 



Respiratory Sounds. During respiration sounds are 

 produced by which the skilled physician can tell much as 

 to the condition of the respiratory organs. 



The Control of Respiration. Breathing is an involun- 

 tary act. Still we can modify it. We can hold the breath 

 for a time ; but it is stated that one cannot hold the breath 

 long enough to produce death by suffocation. 



The muscles of respiration are under the control of 

 nerves. The center of respiratory control is believed to 

 be in the lower portion of the spinal bulb. This respira- 

 tory center is one of the most vital points in the body, for 

 if it is destroyed, breathing is completely stopped, and 

 death ensues. This center is affected by the condition of 

 the blood. For instance, if the blood going to this center 

 has not enough oxygen, the center hastens the process 



