1867.1 



255 



[Wyman. 



The same is true of the north and south curves when the paper is 

 folded on its transverse axis. 



Fig. 6. 



The distribution of particles just described, corresponds, first, to all 

 that we designate as right and left in normal development ; second, to 

 all that v/e designate as fore and hind with reference to the long axis 

 of the body, and which is characterized by symmetry in structure. 



Not only is there this analogy between the distribution of matter 

 around a magnet, and that around the nervous axis of the normal 

 embryo, but the analogy is still more striking in the curves formed by 

 the combined action of two adjoining magnets and the appearances 

 found in more or less double monsters. 



If two magnets are placed parallel to each other, and at a distance, 

 two sets of curves are formed as in the usual way ; but if they are 

 brought so as to be within each other's influence (Fig. 6, B), the two 

 magnetic figures are combined, and now form a single compound one, 

 the middle portion of wliich consists of the curves from the two adjoin- 

 ing sides of the magnets; and the particles from either series of curves 

 do not pass beyond the line where the forces of the two magnets are in 

 equilibrium, but are deflected upwards or downwards, north or south. 

 In this manner that portion of the figure formed by the particles ar- 

 ranged between the two magnets becomes symmetrical, one half 

 consisting of particles belonging to the right magnet, and the other 

 half of those belonging to the left. Tlie symmetiy of the whole 

 compound figure thus formed is in all respects as perfect as that of 

 the ordinary figure from a single magnet. If such a compound figure 

 is projected on paper, and this be folded on either the longitudinal or 

 transverse axis of the wJwle figure, the opposing halves will corres- 



