Forces exerted between Cells 



73 



Fig. 34 represents a series of spheres arranged in a circle. Each 

 sphere has its actual centre indicated by the black spots g, </.... 

 And each sphere is supposed to be made partly at any rate of living 

 material and to have a centre from which it exerts an attractive 

 force upon its neighbours. This centre, b, b... is shown not to 

 correspond with the actual centre, but to lie near the internal pole 

 of the spheres forming the upper part of the diagram, and nearer 

 to the outer margin in the spheres forming the lower part of the 

 diagram. 



Under these circumstances the form taken by the ring of 

 spheres would not be a circle, but one side the lower side would 

 be invaginated within the upper provided that the attractive 

 force between cell and cell (contiguous cells) is strong enough. 



Fig. 35. Parallelogram of forces concerned in the invagination of 

 a circle of spheres such as shown in Fig. 34. 



Fig. 35 illustrates in detail the action of the forces exerted 

 between cell and cell of the lower part of the diagram. 



Instead of taking the whole lower part into consideration, 

 I have taken only three spheres, in the middle one (Y) of which 

 the centre of attraction (A) is shown to be near to the outer 

 margin of the circle while in the two side ones (X and Z) it is co- 

 incident with the centre of the spheres at B and C. 



The parallelogram ACDB will be the parallelogram of forces 

 exerted upon A by the attractive powers of the spheres X and Y, 

 and Z and Y. The lines AB, AC, may be taken to represent the 

 direction of these forces and the line AD the resultant. 



If the tissues are perfectly compressible the sphere Y must 

 move in the direction of D. 



