610 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
of important facts. The consideration of their history leads to the 
irresistible conclusion that the whole period in which the fossiliferous 
rocks were laid down must he multiplied several times for the later 
history alone. The period thus obtained requires to be again increased, 
and perhaps doubled, for the earlier history. 
Anlage and Variation.* — Prof. R. Virchow begins a lecture on this 
subject by pointing out that the pathologists, since Morgagni’s time at 
least, have been more setiological than most of their brethren. Inquiry 
into causes, external and internal, has never been far from them. After 
considering the distinction between external causes, such as Bacteria, 
and internal causes (viz. Diatheses or Anlagen), Virchow distinguishes 
three kinds of Anlage : — (1) Those appearing in extra-uterine life or 
after birth ; (2) those appearing during intra-uterine or foetal life ; and 
(3) those inherited in the strict sense, i.e. dating from conception. 
Moreover, the Anlagen may have a visible structural expression, or they 
may be visibly expressed only in altered function. Variations may be 
distinguished (1) as primary and individual, and (2) as secondary and 
inherited. The former are modifications due to external causes; the 
latter, though evoked under appropriate environment stimuli, are of 
germinal origin. After a brief historical survey of cellular biology, 
Prof. Virchow proceeds to give pathological illustrations of his posi- 
tion, showing how Anlagen are induced by variation, metaplasis, and 
heterotopy. 
Hereditary Polydactylism.t — Dr. Gregg Wilson has collected a 
number of very interesting cases of polydactylism. Thus one family 
history shows a persistence of the abnormality through six generations, 
an increase of the abnormality in the first four generations, and a change 
in position of the abnormality from the post-axial to the pre-axial side 
of the limb. In another case a man with extra minimi on both feet had 
one son with extra great toes, and another son with extra minimi on the 
hands and a double middle toe on one foot. In most cases the abnor- 
mality is very constant in position, though not in degree. 
The author discusses the leading theories suggested in explanation. 
(1) To the atavistic theory the objections appear insurmountable. 
(2) The possibility of accounting for ordinary polydactylism by the 
action of external influences, such as mechanical pressure of the amnion, 
may account for some facts, but it does not explain, for instance, the 
gradual and symmetrical increase of the abnormality in successive 
generations. (3) It remains to fall back upon a theory of germinal 
variation. Weismann supposes that excessive local nutrition causes the 
duplication of the group of determinants representing the part that is 
doubled. This Dr. Wilson modifies slightly by assuming that there is 
variation in the determinants that affect the nutrition of the parts involved. 
Thus, what is transmitted is the nutritive variation. Two figures taken 
by Rontgen’s process illustrate the paper. 
Chemical Basis of Specific Characters.! — Prof. Huppert directs at- 
tention to the specific chemical peculiarities which distinguish organ- 
* SB. K. Preuss. Akad. Berlin, 1896, pp. 515-31. 
t Journ. Anat. and Physiol., xxx. (1896) pp. 437-49 (2 figs.). 
X ‘Ueber die Erhaltung der Art-Eigenschaften,’ Prag, 1896; Biol. Ceniralbl.. 
xvi. (1896) pp. 750-2. 
