560 



Dr. R. Norris on the passage of 



[June 15, 



there exists a free opening into it at its upper part, which becomes 

 suddenly sealed up by cohesion of the sides of the film at the moment 

 preceding detachment ; and this detachment is seen to be a repetition of 

 what takes place in the formation of the primary film. 



The next point to which I wonld draw attention is the power possessed 

 by these films to repair breaches of continuity that may be made in them 

 subsequently to their formation. If any rigid body be wetted, it is quite 

 possible to thrust it through one of these films, move it about, and again 

 withdraw it without interfering with the integrity of the structure, as may 

 be proved by passing a smooth bulbous rod of glass through the film. It 

 is not, however, essential that the body should be either smooth or regular, 

 for the same thing may be done with the naked fist and arm. 



I have demonstrated elsewhere that the blood-corpuscles undergo a 

 mode of aggregation in obedience to progressive mutual attraction in pre- 

 cisely the same fashion as soap-spheres, — that is to say, if they touch at any 

 one point they gradually, by the operation of double cohesion (capillary at- 

 traction), convert each other into polyhedral-shaped bodies*. If we wet 

 any smooth rigid surface and allow one point in the circumference of a 

 bubble to impinge against it, we find that it becomes so drawn down to the 

 plate in every direction, from this point as a centre, as to take on a hemi- 

 spherical form. But if for the rigid surface we substitute a delicate flowing 

 film, such as the soap-film, and allow the bubble to come in contact with 

 it at one point, taking care that there is a free supply of liquid upon its 

 exterior at this point, we observe that the result is different. In this case 

 the soap-sphere takes on the form of two watch-glasses in apposition at 

 their edges, one of the curves being present on each side of the film. The 

 soap-sphere has, in fact, penetrated the film, and arranged itself so that 

 half is on one side and half on the other. 



Now this is precisely analogous to what takes place with the capillary 

 when the corpuscle has entered into cohesion with its wall ; " a protube- 

 rance is seen on the outer surface.'' 



If we can subject this soap- sphere to pressure on one side only, we shall 

 cause it to protrude through the film still further ; this we can do by 

 forming one sphere within another. This inner sphere protrudes more 

 than in the case of the simple film. That there is pressure within a bubble 

 may be known by the fact that, if left with an aperture in it, it will gradu- 

 ally force out the contained air and become again a simple film by its 

 Strong cohesive tendency. 



Further, it will be seen that we can with the greatest ease separate these 

 cohering spheres, bringing them bodily through the film without injury to 

 one or the other ; and this may be taken as a parallel case to the passage of 

 the nucleus through the capsule of the corpuscle, and of the corpuscle 

 itself through the capillary wall. 



I have previously shown that the corpuscles are amenable to the same 

 * Proceedings of Eoyal Society, vol. xvii. p. 429. 



