42 PHYSIOLOGY OF MUSCLE AND NERVE 



motion to the organism as a whole or cause bodies to move with 

 which they are brought into contact. Thus, the cilia lining the upper 

 digestive tract of the frog, beat in the direction of the stomach so 

 that those small particles which are beyond the reach of the process 

 of deglutition, are nevertheless projected into this organ. In the 

 respiratory passage, their effective stroke is directed toward the mouth 

 with the result that the air-passages are constantly cleared of dust 

 and mucous globules. In the female genital tract they beat in the 

 direction of the external orifice, and thus exert a stimulating action 

 upon the spermatozoa, forcing them to progress directly against the 

 ciliary stream. In those protozoa in which the entire external surface, 

 or parts thereof, are beset with cilia, they impart a motion to the 

 entire organism in a direction opposite to that of their effective stroke. 

 They act in this case in the manner of the lateral fins of the fish. As 

 far as the work performed by the cilia is concerned, little can be said. 

 Jensen 1 states that the cilia of a paramecium possessing a length of 

 about 0.25 mm., are able to raise a weight of 0.00158 mgr., or about 

 nine times the actual weight of one of these cells. 



Muscular Movement. In the higher forms, all motions, as well as 

 the movements occurring inside the body, are carried on with the help of 

 specialized cells forming the so-called muscle tissue. These elements 

 appear first of all in the infusoria, such as stentor and vorticella. If 

 one or the other of these organisms is observed under the microscope, 

 its protoplasm will be seen to be permeated by a number of long 

 extended fibrillae, the so-called myoids. In stentor, these fibrillse 

 are arranged singly below the surface of the trumpet-shaped body, 

 while in vorticella they are cemented together to form a thick stalk 

 upon which the bell-shaped upper portion of this organism is situated. 

 When in a condition of rest, their long bodies extend far out into the 

 medium. Upon stimulation their head portions are swiftly retracted 

 toward the surface to which they are attached. This change in 

 their shape and position is made possible by the contraction of these 

 elementary muscle cells. 



Broadly speaking, these contractile fibrillae reappear in the higher 

 animals in the shape of the smooth or non-striated muscle cells. Be- 

 sides, a second type of cell is found here which possesses a much greater 

 complexity of structure and forms the chief constituent of striated mus- 

 cle. The first enter very largely into the formation of what might be 

 termed the visceral musculature which performs work in the interior 

 of the body, while the latter constitute the skeletal musculature which 

 is concerned with the regulation of the position of the animal in space. 

 The striated is under the direct control of the will, while the non-striated 

 is not, and has to do solely with the vegetative processes of life. Be- 

 sides these, the animal body also contains a third type of contractile 

 tissue, namely the cardiac muscle, but the function of this one is 



1 Pfluger's Archiv, liv, 1893, 537. 



