THE PHYSIOLOGY OF EXCRETION. 87 



This interruption between the proper balance of cohesion 

 and adhesion is similarly the cause of the mechanical disinte- 

 gration of the excretophores. During their wandering toward 

 the epidermis these cells have to pass through narrow spaces 

 between the muscle-bundles which lie underneath the skin. 

 These spaces are irregular in shape, in some places wide, in 

 others extremely narrow, and we can easily understand that in 

 the narrow places a great resistance is presented to the excre- 

 tophores. The latter try to overcome this obstacle by sending 

 forth exceedingly fine pseudopodia, which are able to pass 

 through the narrowest spaces, and may enlarge again after they 

 have passed. In the narrowest spaces friction or adhesion must 

 considerably overbalance cohesion, and it is evident that a 

 separation of the pseudopodium from the nucleolated cell body 

 may easily take place there. 



These detached pseudopodia will continue to move for some 

 time, and will even reach the epidermis. It is here that the 

 second phase of disintegration takes place, — the final chemical 

 disintegration. The causes of this disintegration are evident. 

 We know that the nucleus exercises ^ 



chemically a balancing effect upon the ^^^If^^i'-'-'tP 



substances of the cells. As soon as the A.fiiU'-.A-jwr 



nucleus is removed the balance is de- (M'-^'^i^^ 

 stroyed and the chemical disintegration ^ ^ ^^3^fM^ 

 sets in. 



Fig. 2 shows in a diagrammatic way 

 the changes which take place in the de- 

 tached parts of an excretophore. The 

 cytoplasmic {cp) netwjDrk becomes less and 

 less distinct, till finally not a trace of it 



is left. The isolating drops get gradually smaller and darker 

 in color ; at the same time a number of large colorless drops {d) 

 are discharged from the remains of the excretophores, and finally 

 there is nothing left but a mass of very small, dark granules (/). 



It seems to me that as soon as the proper relationship 

 between the substances of the cell is unbalanced a number of 

 noxious substances, as bases, etc., are secreted in the cyto- 

 plasmic lymph, which dissolve both the cytoplasmic threadwork 



