236 MUSCULAR SYSTEM. 



much an active effort as contraction, in the organic mus- 

 cles; the powers of both are s6 intermingled as not to be 

 separable. 



Development of the Muscular System of Organic Life. 



Q. Is it the action of the brain at birth which sets the 

 ' organic muscles into activity ? 



e#. The principle has been adopted that these muscles 

 are independent of the brain. 



Q. What causes then excite them? 



<&. One cause is sympathy with the external skin, which 

 is irritated by the contact of air at birth; another is, the 

 excitement on the beginning of the mucous surfaces, and 

 on the whole lungs, in breathing. Other causes are fluids 

 taken into the stomach, the red. blood penetrating the or- 

 ganic muscles, instead of fetal black blood; and lastly, the 

 meconium stimulates the bowels. 



Q. Does growth in the external parts, and in the or- 

 ganic muscles, cease at the same time? 



ft. No; each part has its period of full growth; the or- 

 ganic muscles are longer in attaining this than others. 

 The organic muscles are not subject to the irregularities 

 of growth, that so remarkably characterize the animal 

 muscles. 



Q. Why do nutrition and growth vary in different tex- 

 tures? 



#. Because they depend on the vital forces, which vary 

 in every tissue. 



Q. Which of the muscular systems is soonest exhausted? 



#. Both in exercise and life the animal muscular sys- 

 tem is soonest exhausted. 



