The New York herald., 1922-07-23
Bruce Lowe Formula and Eng
lish Stud Book Rule Shat
tered by Microscope.
SECRET OF GERMAN PLASM
Experiments and Deductions
of Importance to Students
of Species.
BY GURNEY c. CUE.


Hard headed horsemen have always
looked askance at the Bruce Lowe
theory of speed Inheritance, which
places more Importance on the So
called tap root mare, perhaps twenty
generations away in racing pedigree
than in the immediate parents of a
horse. 1t has remained for science
and the microscope, however, to dem
onstrate the fallacy of the Australian
trrfman's discredited conclusion.
Out at the Eugenics Record Office in
Cold Spring Harbor, Long Island, Prof.
Charles B. Davenport. Dr. II. III. Laugh
lin and other experts in heredity have
been making special study of the rate
of elimination of mongrel blood In the
process of grading up" by the use of
pure bred sires in importing the live
stock of the country. And so success
fully have they pried into the secrets
OF nature that as to many breeds OF
animals they are now able to state the
exact number of generations necessary
to completely eliminate all trace of the
tap root female or foundation stock.
whether her blood Is pure" or impure"
Theoretically there would always be
q fraction of mongrel blood in each in
dividual of a herd or group produced by
the pure sire method. regardless OF the
number of generations to which the
process might have been carried" DIR.
Laughlin said in recent paper read
before the Society for Experimental
Biology and Medicine. 'As matter
of practice. however. it is known that
after few generations the progeny OF
the pure sire method are admitted on
equal terms into the variety or species
OF the pure sire. and with no apparent
injury to the purity Of the paternai
race In man, as in other animals, the
germ. pasm is not indefinitely dilutable
but segregates into chromosomes which
in their entirety either do or do not
pass from a given ancestor to the Off
spring.
Chromosomer Control.
DR.. Laughlin's explanation Of the ex-
perinlents and mathematical calcula-
tions on which these statements are
based is extremely technical in termi-
nology and otherwise. 1t would be diff
cult, IL not impossible, for any one with
out more than smattering of biologi-
cal lore to follow 1t. but the gist of it is
that the number of crosses necessary
to eliminate the last trace of mongret
blood by the use of successive pure bred
srcs depends almost wholly upon the
number of chromosomes I'm the germ
coils of the species to be improved
Chromosomes are the carriers of the
hereditary traits. In man, where the
number of chromosomes Is twenty y-four
the process is practically complete after
five generations; that Is, its continue
ton then ceases to be practically effec-
he chs N
will possess absolutely no chromosomes
descended from the original mongrel
lam Is as thousand to one.
Unfortunately the number Of chromo-
zones characteristic of the horse has
never been ascertained. The process in
wolves considerable difficulty and an
expense of 5000 or $500, and for finan-
cial reasons alone has been neglected
at the biological laboratory In Cold
Spring Harbor. This is the more to be
regretted because the laboratory was
founded by John D. Jones, whose family
was conspicuously identified with trot-
ting and racing on Long Island for more
than century, while the Eugenics
Record Office, situated on this Jones
family estate, was built by Mrs. z. III.
Hartman. to whose interest in horses
Orange county owes it's present prom
inence in harness racing.
Discoveries OF Practical Value.
The scientific discoveries Of Profess
sor Davenport and his associates in the
biological laboratory and the Eugenics
Record Office assume practical impor-
tance in horse breeding when it Is re-
membered that the English Jocky Club,
which controls the English stud book
for thoroughbred racehorses, made a
ruling ~not many years ago excluding
from registration therein all horses
whose ancestry is not traceable in every
line to animals registered in the orig
inal volume with perhaps twenty or
more uncontamnated crosses. This rule
has operated to throw out many or our
great American racing families tracing
TO Lexington and other "short bred
sires, and would exclude at least three
winners Of the Epson Derby as well as
numerous other, horses of the highest
class. II has been the subject of scath-
ing criticisms from nearly every coun-
try where racehorses are bred and
raised, and has even resulted IN So
called half bred stud book In the
light of recent research, however. the
PREMISES on which the English rule was
based are false, and most OF the horses
in the book for half breds are OF as
pure heredity as those in Weatherby's.
Wncn go Ddck twenty bcHei atiohS AZ
every direction without break.
American horsemen have reason to
be particularly pleased with the findings
of the biologists Owing to the fact that
connparatively few racehorses here In
carly days could be traced back in every
line to imported English stock. 1t be-
came necessary to fix upon the number
o. OF crosses from thoroughbred sires
necessary TO constitute thoroughbred
horse. Acting solely on observation and
experience in racing. IL was decided that
any horse having five such crosses ought
10 be deemed thoroughbred himself,
end this long observed custom was
recognized in the compilation OF all our
American stud books. Now that the
exact number of crosses necessary TO
eliminate every ancestral chromosome
OF monogrel or foreign blood can be
ascertained with scientific precision,
the Jockey Club as custodians of the
American stud book. might strengthen
the foundation on which II rests and
perhaps pave the way for repeal OF the
exploded English rule by appropriating
the necessary sum to defray expenses
in working out the problem at Cold
ksprfng Harbor.