94 NORMAL HISTOLOGY AND ORGANOGRAPHY. 



Voluntary muscles, while more powerful, tire easily. 

 Plain muscle has a wonderful endurance. The 

 pain produced by violent action of plain muscle is 

 in direct proportion to the degree of contraction. 

 Some examples are : the colicky pains of the intestine ; 

 labor pains ; pains due to calculi in the ureter or bile 

 duct; or the pain in appendicitis produced by con- 

 traction of the plain muscle of the appendix. These 

 pains have many things in common They may 

 last for hours, they remit and recur with regularity, 

 and they come in waves. 



An infection in a muscle, as a psoas abscess, bur- 



Nucleus and nucleolus. 



Neurilemma. Medullary sheath. 



I I | 



I I 



Axis cylinder. Node of Ranvier. 



Collateral. 

 Dendriles. 



Fig. 60. Diagram of a neuron. 



rows in the fascia, that is, spreads along the con- 

 nective-tissue septa, perimysium and endomysium. 

 The quality of meat depends on the amount of con- 

 nective tissue. In tough meat the fasciculi are 

 coarse and perimysium abundant. In tender sir- 

 loin the reverse prevails. 



IV. NERVOUS TISSUE. 



Nervous tissue is most highly specialized of all 

 tissues and consists of elements called neurons. A 

 neuron is a nerve cell with all its processes. These 

 cells vary greatly in size; usually they are large. 



