7 o8 THE PHYSIOLOGY OF THE CONTRACTILE TISSUES 



can be calculated by removing the membrane, fixing it on a plate 

 of glass, cilia outwards, putting weights on the glass plate, and 

 allowing the cilia, like an immense number of feet, to carry it up 

 an inclined plane. Bowditch found in this way that the cilia on 

 a square centimetre of mucous membrane did nearly 7 gramme; 

 millimetres of work per minute (equal to the raising of 7 grammes to 

 a height of a millimetre). 



Since the cilia in the respiratory tract all lash upwards, they 

 must play an important part in carrying up foreign particles taken 



in with the air, and the mucus in which 

 they are entangled, as well as patho- 

 logical products. Engelmann found 

 that the energy of ciliary motion in- 

 creases as the temperature is raised 

 up to about 40 C, after which it 



Fig. 234. Ciliated Cell (M. 

 Heidenhain). From a 

 ' liver duct ' of the garden 

 snail x 2,500. 



-6 



Fig. 235. Ciliated Cell (Schneider). 

 From a flatworm (Planocera folium). 

 i, space between two adjoining 

 ciliated cells; 2, basal bodies; 4, 

 inner granule ; 5, ' cilia roots ' ; 

 6, boundary layer. 



diminishes quickly. Over- heating causes cilia to come to rest, but 

 if the temperature has not been too high, and has not acted too 

 long, they recover on cooling, thus exhibiting the phenomena of 

 heat standstill which we have already studied in the heart. 



It is not well understood in what way the contraction of the cilia 

 depends upon their connection with the body of the ciliated cell. Very 

 few cases occur in which cilia have the power of independent motion 

 when severed from the cell-body. It has been observed in certain low 

 forms of animals that cilia which have been broken off from the cell 

 are still able to contract when a small portion of the substance of the 



