552 _ Dr. M. Hartog. | Dec! i 
by Ziegler,* who devised an ingenious magnetic model, too simple, however, 
to carry theory much further; and especially by Gallardo,} whose electro- 
static model was a great step in advance. It consisted in the introduction 
of the poles of an electrostatic machine into a glass trough containing 
sulphate of quinine suspended in oil of turpentine. The quinine segregated 
out in filaments, or chains, forming a spindle between the terminals, so 
that the behaviour of “chains of force” (see p. 555) might be studied. He 
also showed that the introduction of a third terminal put to earth produced 
a deviation of some of the fibres from the belly of the spindle to itselfi—the 
figure being, in fact, a “ triaster,’ such as sometimes occurs in dividing cells. 
The adverse criticisms on Gallardo’s paper showed clearly that biologists 
for the most part had but ill-defined ideas of the action of dual forces, and 
the application of their laws to the conditions of the cell. As mentioned 
above, the necessary conception of the “ material chains of force” had not even 
been stated by the physicist ; and the conception of differences of permeability 
had not yet been applied—even by Ziegler and Gallardo—to cytological 
substances. These were first put forward in my Preliminary Note “ Des 
Chaines de Force, et d’un nouveau Modele magnétique des Mitoses 
cellulaires.”? 
V, 
To render the actual experimental study intelligible to the biologist, we 
must review the conception of “lines of force” and its two extensions just 
mentioned. Faraday, unable to admit the possibility of action at a distance, 
suggested that wherever such appeared to take place between two bodies or 
centres, the intervening medium must be in a state of strain: the direction of 
the stresses and consequent strains centering round the interacting bodies, 
and being continuous from one to the other along lines which he termed 
“lines of force.” 
Clerk Maxwell, who much extended the idea, gave this definition :—“If we 
électro-magnétiques dans le noyau. Peut-étre arrivera-t-on 4 mettre expérimentalement 
en évidence ces curieux processus en employant des sphéres liquides en suspension dans un 
autre liquide, comme le faisait Plateau, mais en mélangeant ces liquides de substances 
fortement magnétiques et capables d’acquérir des pdles sous ]’influence d’aimants puissants. 
Il y aurait tout un ordre de recherches 4 entreprendre dans ce sens.” (‘ Bull. Sc.,’ vol. 7, 
1876, p. 258.) I think it right to cite this passage, as the periodical is not widely circulated 
in England, and the passage, to my knowledge, is rarely quoted ; I blush to say that I first 
read it in Gallardo. It clearly foreshadows the line of work pursued by Gallardo and 
myself. 
* “Untersuchungen tiber die Zelltheilung,” ‘ Verh. Deutsch. Zool. Ges.,’ 1895. 
t “Gallardo, “Essai d’Interprétation des Figures karyokinétiques,” ‘Ann. Mus. 
Buenos Aires,’ 1896 ; “ Interprétaciédn dindmica de la Division Célular,” 1902. 
{ ‘Comptus Rendus,’ June 10, 1904. 
