190 THE ARMY FOR HOME DEFENCE 



and we have no means of measuring the amphtude of their beat. 

 The frequency is somewhere about 10 per second. One may say 

 that the energy necessary for an effective stroke would be directly 

 proportional to the amplitude and to the square of the velocity. 

 E = k.sv^ (where k is a constant, s the amplitude, and v the velocity 

 of stroke). Therefore the work done in an effective (unloaded) 

 stroke would be ksv^/t, where t is time, or as 



s 1 



W = kv\ 



The value of TF varies from almost to probably just under 30 ergs. 

 The activity of the cilia is modified by almost any factor that 

 modifies protoplasmic activity. The relative concentrations of 

 oxygen, carbon dioxide, hydrogen ion and various salts are factors 



any alteration of which will cause 



^ a change in activity. Increase of 



Ifelrf j jif^ temperature up to a critical value 



^ . i. " causes increased activity. Especially 



^ interesting is the alteration produced 



in rhythm and rate by loading the 



^ C^ cilia. The placing of an inert 



"^^ powder on the mucus-covered tips 



Fig. 45. — To demonstrate turgor. The . rs:? • j_ . • . , • n i 



sausage-shaped membrane filled with a sugar IS SUIUCient tO CXCltC actlVC nagcl- 



solution is flaccid. When immersed in water, , . 



endosmosis recurs and the vessel becomes latlOU. 



We have no evidence as to the 

 mechanism involved in the production of this movement. Schafer 

 supposes an increase in liquid pressure in a hollow blind tube 

 (cf. Fig. 45 and Expt. 6 Part II.,), but gives no explanation as 

 to how this alternate flow and ebb of pressure into the cilia is 

 produced. 



2. Reticulo-endothelial System. It has been found that when a 

 substance like the dye, lithium carmine, a colloid, is injected into 

 the blood stream of a living animal, it is not immediately excreted 

 nor is it uniformly distributed throughout the tissues. Muscle 

 fibres, ganglion and glial cells appear to take up none of the dye, 

 while (in the cat) about two-fifths is found in the liver, half in the 

 lungs, one-twentieth in the spleen, and the remainder in large part 

 in the kidney, lympoid tissue, and certain cells moving freely in 

 the blood stream, the true vascular endothelium being stained very 

 feebly. If, instead of killing the animal for examination an hour 

 after the injection, the animal were allowed to live for about twflve 

 hours, then most of the dye would be found in certain cells of the 

 liver. The cells which are capable of ingesting colloidal particles 



