574 THE FORMS OF TISSUES [ch. 



In like manner, if we have a spheroidal body less than a hemi- 

 sphere, such for instance as a low, watchglass-shaped cell (Fig. 

 225, A), it is obvious that the smallest partition by which we can 

 divide it into two halves is (as in our flattened disc) a median 

 vertical one; jand likewise, the hemisphere itself can be bisected 

 by no smaller partition meeting the walls at right angles than that 

 median one which divides it into two similar quadrants of a sphere. 

 But if we produce our hemisphere into a more elevated conical 

 body, or into a cylinder with spherical cap, there comes a point 

 where a transverse horizontal partition will bisect the figure with 

 less area of partition-wall than a median vertical one (C). And 

 furthermore, there will be an intermediate region, a region where 

 height and base have their relative dimensions nearly equal (as 



Fig. 225. 



in B), where an oblique partition will be better than either 'the 

 vertical or the transverse ; though here the analogy of our triangle 

 does not suffice to give us the precise hmiting values. 



We need not examine these hmitations in detail, but we must 

 look at the curvatures which accompany the several conditions. We 

 have seen that a film tends to set itself at equal angles to the surface 

 which it meets, and therefore, when that surface is a sohd, to meet 

 it (or its tangent) at right angles. Our vertical partition is, there- 

 fore, a plane surface, everywhere normal to the original cell-walls. 

 But in the taller, conical cell .with transverse partition, the latter 

 still meets the opposite sides of the cell at right angles, and it 

 follows that it must itself be curved; moreover, since the tension, 

 and therefore the curvature, of the partition is everywhere uniform, 

 it follows that its curved surface must be a portion of a sphere, 

 concave towards the apex of the original cell. In the intermediate 

 case, where we have an obhque partition meeting both the base 

 and the curved sides of the mother-cell, the contact must still be 



