904 
SCIENTIFIC BOOKS 
Vergleichende Anatomie des menschlichen 
Gebisses und der Zihne der Vertebraten. 
Von Dr. Paut pE Terra. Jena, Fischer. 
1911. Pp. v+ 451. Mit 200 Textabbil- 
dungen. 
Thoroughly Germanic is the stamp of this 
work: in its tireless massing of details, in its 
bibliography of three thousand titles and no 
less in its comparative anatomy. 
The author, Dr. Paul de Terra, “vorm. 
Zahnartzt in Ziirich,” has not been content to 
regard the human dentition solely as the sub- 
ject matter of a lucrative profession, but con- 
ceives odontology rather as a branch of mor- 
phological science. After a section devoted 
chiefly to the masticatory apparatus of verte- 
brates and to the development of the mouth 
cavity and its parts we find an apparently 
reliable account of the dentition in general, 
dealing with the macroscopic and microscopic 
form, the development and calcification of the 
milk and permanent dentitions, the mechanism 
of replacement, the reduction and degenera- 
tion of teeth, supernumerary teeth, chemical 
composition of the dental elements and the 
like. 
The author is of the opinion that odontology 
is still very largely an empirical science with 
no great number of well-founded doctrines. 
He says it is difficult, in view of the multitude 
of controversial matters, to write a consistent 
text-book of odontology. He has, therefore, 
striven to state all sides of the controversial 
questions with great impartiality. This is 
perhaps the reason why matters relating to 
evolutionary origins are left in such great 
uncertainty and why the now well-discredited 
and thoroughly archaic hypothesis that the 
molars of mammals arose through the con- 
crescence of single peg-like teeth is treated 
with so much respect. 
The “theory of trituberculy ” is very briefly 
expounded, but without help from Osborn’s 
later researches, especially “The Evolution of 
the Mammalian Molar Teeth,” 8yo, 1908, 
which the author does not quote even in his 
bibliography. It is to be hoped that some day 
writers of text-books on zoology and odontol- 
SCIENCE 
[N.S. Vou. XXXV. No. 910 
ogy will become aware that the strong and 
well-founded part of the theory of trituberculy 
is not the view that the tritubercular molar 
arose from the triconodont and protodont types 
through “migration of the cusps”—a view 
that rests upon the slenderest of analogical 
evidence. 
Another desideratum is the final rejection 
of one of the early trituberculy diagrams (re- 
produced on page 62 of the work under con- 
sideration) which has unfortunately gained a 
wide currency in text-books. This diagram, 
which purports to show the spatial relations of 
the cusps of the upper and lower molars when 
in contact, is thoroughly misleading. because no 
teeth known fit together in the way there rep- 
resented. In every tritubercular-tuberculo- 
sectorial dentition, as well as in derived types, 
the protocone of each upper molar fits squarely 
into the talonid and behind the trigonid of the 
corresponding lower molar; as the hypocone is 
developed it reaches into the valley of the 
trigonid of the next following lower molar. 
Primitive Marsupials, Rodents, Insectivores, 
Carnivores, Primates, “Ungulates” of all 
orders, all conform to this rule, which fur- 
nishes a complete clue to the spatial relations 
of all parts of the upper and lower molars 
when in contact. As the reviewer has else- 
where shown, this fact has an important bear- 
ing on the derivation of the tritubercular 
dentition. The alternating relationship of the 
parts of the upper and lower molars was prob- 
ably established very early in the history of 
the Mammalia and is indeed clearly fore- 
shadowed in some of the extinct mammal-like 
reptiles of South Africa (e. g., Diademodon, 
Sesamodon). 
It is unfortunate that the author with all 
his diligence should have made so little 
effective use of contemporary vertebrate pale- 
ontology which might have furnished him with 
a well-organized method of interpreting at 
least in part his great compilation of undi- 
gested facts about the dentition of fishes, 
amphibians, reptiles, birds and mammals, a 
subject covering about 200 pages of the present 
work. If one wishes to know how many teeth 
