610 REPORT—1904. 
3. On the Elucidation of Cellular Fields of Force by Magnetic Models. 
By Professor Marcus Harroe. 
The structure developed in the protoplasm of a dividing cell suggests so 
strongly the magnetic field of force of two unlike poles that the analogy struck 
the earliest observers. Nevertheless, certain phenomena have remained unex- 
plained by the assumption that the force was analogous to a ‘dual force’ 
(Faraday), such as magnetism or electricity; and some have been alleged to 
be absolutely incompatible therewith. It was therefore essential to supplement 
physical theory as more or less incompletely stated and understood by actual 
experiment, 
The field of force revealed by agitating paper strewn with magnetic dust over 
the poles of a magnet is, we may say, a statical field, and can only have distant 
analogies with the changing field formed in viscid protoplasm, differentiated into 
strands and medium, the former more permeable, the latter less permeable, clearly, 
to the forces involved. To obtain a closer analogy I suspend magnetic dust in a 
viscid liquid (balsam, glycerine, melted jeily), and place the mixture in a trough 
or spread it on a plate above the poles of one or more electro-magnets, or their 
m-re cores of soft iron. We obtain in the apparatus a thin axial section of 
such a field as would be given by detached magnetic poles; and with these 
arrangements I have obtained many variants from the text-book figures. 
In any mixture the magnetic particles sort themselves out into what we may 
term material ‘ chains of force,’ following the directions of the lines of force and 
containing within them more of these lines than the relatively impermeable 
medium. Such chains of force may be deflected by currents, gravity, &c., and 
still carry within them a proportion of their lines of force not much diminished in 
the conditions of the experiment ; for their elongation is of a much lower order 
than the ratio of the permeability of their material to that of the medium, The 
more important variants, comparable to the achromatic figures, of the cell realise 
many of the very conditions which have been regarded as incompatible with a 
dual force. They are illustrated by photographs of the magnetic fields compared 
with analogous cytoplasmic fields. 
Variant 1.—In an unlimited magnetic field of two unlike poles all the lines of 
force tend to meet, and are concave to the interpolar axis. On limiting the field 
by a permeable boundary, such as an oval vignette mask of soft iron, the outer 
rays straighten out, or even become convex to the interpolar axis, and turn their 
backs on the rays joining the poles. In this way we get a closer approximation 
to the differentiation of the cell-figure into a dumbell, with circumpolar asters 
and interpolar spindle. From this we may infer that the Hautschicht of the 
cell is permeable to the force in operation (the nuclear wall appears to be also 
permeable). 
Variant 2.—If the magnetising force be sufficiently intense to overcome the 
viscidity of the medium, the chains of force do not retain their primitive even 
distribution ; but the interpolar chains move laterally towards the axis, becoming 
denser as they do so: like all movable conductors, they tend to place themselves in 
the most intense portion of the field. In this way they give an additional 
differentiation into spindle and asters, leaving on either side of the spindle a clear 
space comparable to what has been termed ‘ Biitschli’s space’ by Rhumbler. 
Variant 38.—If our plate be slowly rotated over the poles the chains become 
spiral, or, more accurately, sigmoid—|-shaped ; this would be the section of an 
ovoid of revolution with spiral poles, such as were first figured by Mark in the 
segmentation of the slug (Limax). Such figures may be fixed if the medium he 
melted jelly or balsam. 
Variant 4,—Fven in the published figures formed on paper the material chains 
of force are frequently seen to anastomose—an impossibility for the Zines of force 
in a uniform medium. Owing to the peculiar properties of these chains they often 
interlace in viscid media towards the minor axis of the figure ; z.c., they cross at 
slightly different levels. The’less permeable the medium to the force, the less 
