56 NATURE 
magnetic forces in determining crystalline structure, 
magne-crystallic action, and chemical combination, in 
non-ionised media is apparent. It is interesting to 
note that Pascal (1910) showed that in organic com- 
pounds, all of which are diamagnetic, the molecular 
susceptibility is (apart from certain peculiarities of 
structure common to certain types of compounds) 
equal to the sum of the atomic susceptibilities of the 
component atoms. This is not true of ionised com- 
pounds, such as metallic salts, where the coupling 
between the atoms is probably of an electrostatic 
nature. ’ 
Further developments of the magneton theory were 
made by Parson (1915), who identified the electro- 
magnetic coupling between pairs of magnetic doublets 
with the force of chemical combination. The mag- 
neton, or anchor ring electron, has been applied by 
Allen (1920) to interpret the phenomena of optical 
activity and optical isomerism. In connexion with 
the magnitude of the local magnetic field, namely, 
107 gauss, it is interesting to note that Allen’s calcula- 
tions give a value 108 gauss at a distance from the 
anchor ring equal to its radius. 
A number of attempts to obtain a quantum theory 
of magnetism have been made in recent years by 
Oosterhuis, Keesom, Gans, Reiche, and others. These 
are based on the assumption that the molecules are 
endowed with quantised molecular rotations, but the 
theory of Gans is the only one to take account of molec- 
ular interactions. 
In connexion with these views the theory of Bohr 
and Sommerfeld must be considered. Though this 
has proved so successful in the interpretation of the 
fine structure of spectral lines, it does not appear at all 
obvious how the open elliptical orbits of this theory 
can give the uniquely balanced systems required to 
explain diamagnetism, nor does it give a picture of the 
directed forces which are responsible for crystal 
lattices. These considerations suggest that the atom 
must have a static structure. Perhaps the electron 
itself is quantised, the motion of its parts being highly 
localised compared with atomic dimensions. The 
electrons in an atom may be distributed on spherical 
or ellipsoidal surfaces, and the passage from one surface 
[JANUARY 13, 1923 
to another determine the emission of a definite amount 
of radiation of a certain frequency. ‘ 
Quite recently Whittaker (1922) has published a 
new quantum mechanism of the atom based upon the 
existence of a number of atomic magnetic doublets. 
If an electron collides with this system the collision is 
perfectly elastic if the velocity of the electron is less 
than a certain amount. If the velocity exceeds this 
amount the electron passes through the magnetic 
system and hands over to the latter a definite quantum 
of energy which is identified as Planck’s quantum. 
The derivation of the Balmer series can be obtained 
from this conception ; it may later be found equally 
effective in interpreting the fine structure of spectral 
lines. Allen has replaced the particular magnetic 
structure postulated by Whittaker by a pair of ring 
electrons, thus identifying Whittaker’s model more 
closely with Langmuir’s cubical atom. The atomic 
structure is dynamical locally but is essentially static 
at ranges comparable with molecular dimensions. 
The static structure is required to account for 
crystalline and magnetic properties of matter in 
the non-radiating state. Recent experiments by 
the writer (1922) indicate that the occlusion of 
hydrogen by palladium produces a system the elec- 
tronic configuration of which is similar to that of 
silver, and the fall in paramagnetism of the palladium 
is consistent with this view, silver being diamagnetic. 
Manganese which has been fused in an atmosphere of 
hydrogen is ferro-magnetic, although pure manganese 
is paramagnetic. Iron which has been fused in 
hydrogen has a higher coercive force than ordinary 
iron (like cobalt). These experiments indicate that 
when hydrogen is occluded in one of these elements an 
electronic system is produced corresponding to an 
element the atomic number of which is one higher than 
that of the element occluding the hydrogen. The 
suggestion is that the hydrogen electron, in such 
systems, enters into the outer shell of electrons of the 
metallic atom. 
A static model, consistent of course with a highly 
localised dynamical model, such as the one advocated 
above, seems to be the only satisfactory interpretation 
of these results. 

Obituary. 
Pror. Oscar HERTWIG. 
HE death of Oscar Hertwig, formerly professor of 
anatomy in the University of Berlin and director 
of its Anatomical-Biological Institute, removes from 
the scene one of the chief leaders in “morphological 
science. He formed a link in that chain of illustrious 
men including Johannes Miiller, Gegenbaur, Fiir- 
bringer, and Gaupp, which has demonstrated how 
fully Germany has realised the importance of entrust- 
ing its great chairs of anatomy to men who are anato- 
mists in the broadest sense of the word, leaders in 
vertebrate morphology and not merely experts in 
the details of anthropotomy. 
Hertwig was most widely known through his series 
of admirable text-books. His ‘‘ Lehrbuch der Ent- 
wicklungsgeschichte des Menschen und der Wirbel- 
tiere’”’ made its appearance in 1886 and has passed 
NO. 2776, VOL. 111] 
through numerous editions, both in its extended and 
in its condensed form (‘‘ Elemente,” 3rd Edition, 
1920). ‘‘ Die Zelle und die Gewebe,” first published 
in 1893, and known in its later editions as the “ All- 
gemeine Biologie,” is still widely used as a most 
admirable text-book of general biology on a cyto- 
logical basis. During the years 1901-6 Hertwig 
brought out the various instalments of that wonderful 
encyclopedia which bears the  characteristically 
German title “‘ Handbuch der Entwicklungslehre der 
Wirbeltiere,”’ edited and in parts written by himself. - 
While it is, perhaps, permissible to hope that the 
appearance of this colossal work marks the approach- 
ing end of what may be called the encyclopzdic age 
of biology, in which real progress has become more 
and more impeded and slowed down by the accumula- 
tion of minute details, there can be no question regard- 
i... 
