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TEXT-BOOK OF PHYSIOLOGY 



FIG. 42. THE CURVE 

 OF CONTRACTION OF THE 

 BLADDER MUSCLE AT 

 BODY-TEMPERATURE IN 

 RESPONSE TO A SINGLE 

 INDUCTION CURRENT. 

 THE TIME 'IS INDICATED 

 IN SECONDS. (Stewart.) 



period covered 0.25 second. With other muscles the time relations are 

 slightly different. Tetanization of the bladder muscle of the cat occurred 

 when the stimuli succeeded each other with a certain rapidity; the interval 

 between stimuli approximating a period somewhat less than two seconds. 

 This muscle resp'onds to variations in [temperature, to strength of stim- 

 ulus, to the load, in a manner similar to, if not iden- 

 tical with, the skeletal muscle. 



The Function of the Visceral Muscle. In a 

 general way it may be said that the visceral muscle 

 determines and regulates the passage through the 

 viscus or organ of the material contained within it. 

 The food in the stomach and intestines is subjected 

 to a churning process by the muscles, in consequence 

 of which the digestive fluids are more thoroughly in- 

 corporated and their characteristic action increased. 

 At the same time the food is carried through the 

 canal, the absorption of the nutritive material pro- 

 moted, and the indigestible residue removed from the 

 body. The blood is delivered in larger or smaller 

 volumes according to the needs of the tissues through 

 a relaxation or contraction of the muscle-fibers of the 

 blood-vessels. The urine is forced through the ureter 

 and from the bladder by the contraction of their re- 

 spective muscles. The mode of action of the individ- 

 ual muscles will be described in successive chapters. 



Ciliary Movement. The free surface of the epithelium covering the 

 mucous membrane in certain regions of the body is characterized by the 

 presence of delicate filamentous processes termed cilia. (See Fig. 43.) 

 Ciliated epithelium is found in man and mammals generally, in the nose, 

 Eustachian tube, larynx, with the exception of the vocal membranes, trachea 

 and bronchial tubes as far as the pulmonary lobules, Fallopian tubes, uterus, 

 and epididymis. The lumen of the central canal of the spinal cord and the 

 cavities of the brain are lined, especially in childhood, 

 by cells provided with similar cilia. Ciliated epithe- 

 lium is also found in all classes of animals, and espe- 

 cially in the invertebrates. 



The cilia found in the human body vary in length 

 from 0.003 mm. to 0.005 mm. They are apparently 

 structureless and colorless, and appear to have their 

 origin in and to be a prolongation of a transparent 

 material on the outer surface of the cell material. The 

 number of cilia present on the surface of any individual 

 cell varies approximately from five to twenty-five. 

 When ciliated epithelial cells, freshly removed from 

 the mucous membrane and moistened with normal saline, are examined 

 with the microscope, it will be found that the cilia are in continuous and 

 rapid vibratile movement, so much so that the individual cilium cannot 

 be distinguished. In time, however, their vitality declines and the rapid- 

 ity of movement diminishes. When the movement of the individual 

 cilium falls to about eight or ten per second, its character can be readily 



FIG. 43. CILIATED EPI- 

 THELIUM. 



