266
ABSTRACTS
The symbol ta is suggested for this simple autosomal
recessive character.
Mortality under 4½ days was not classified.
Hence
there is a slight excess of normal over talpid embryos
among those matings where 95 per cent or more of the
embryos could be classified. Actually 23.6 per cent of
the 415 eggs from such matings produced talpid em-
bryos, whereas 25 per cent would be expected of a
simple autosomal recessive. The fewer the deaths
under 4½ days the nearer the agreement between the
observed and expected incidence of the results of the
lethal gene.
Linkage tests were made by examining the linkage of
ta with three of the five known autosomal linkage
groups described by Hutt and Lamoreux. The results
were as follows: 1. If 'ta is in the Cp.R.U. linkage
group, it is not closely linked with r'; 2. The charac-
ter 'ta probably does not belong to the DM linkage
group'; and 3. '
there has been a ratio of parental
to non-parental colours of 83 to 93, as compared to the
expected ratio of 88 to 88 if I and ta were not linked'
in the F I Cr linkage group; this difference is insigni-
ficant. [J. N. W.].
A new type of autosomal nakedness in the domes-
tic fowl, P. D. STURKIE (1942). J. Heredity
33, 202
NAKEDNESS in birds is of two types, viz. that in
which feather follicles are abnormal, although pterylosis
occurs and that in which pterylae are absent.
The
abnormality discussed here is of the latter type. The
expression of the character varies from almost normal
to almost complete nakedness, with degrees of the latter
being rated as grades I, II, III and IV, indicating in-
creasing orders of denudation. The frequency with
which the different grades of nakedness were observed
to occur was in the order II. III, IV, I.
Progeny of a naked male and several heterozygous
sons crossed with normal hens were naked and normal in
very nearly a 1:1 ratio indicating a simple dominant
character. Crosses of F 1 naked females with a normal
male gave naked males and naked females in a ratio
of 1:1, indicating a simple autosomal character. It is
believed that the mutation had occurred only recently
in a female since the character was observed in only
one bird, a male in 5000 which were progeny of
approximately 250 females and 20 males.
Its occur-
rence originally in a male would have resulted, it is
thought, in more individuals being involved.
The hatchability of naked and normal chicks was the
same. In all other respects, except for feathering,
naked chicks were quite normal. There was a high
mortality among naked chicks, however, from 10-15 days
of age and thereafter. The feeding of wet mash seemed
to reduce the death rate in naked chicks so long as it
was fed. When dry mash was substituted the death rate
would increase.
The degree of denudation was not
casually related to death rate. It seems, therefore, that
this character is at least partially lethal. [J.N.W.]
A new type of recessive achondroplasia in cattle.
P. W. GREGORY, S. W. MEAD and W. M. REGAN
(1942). J. Heredity 33, 317
THE appearance of a sub-lethal hereditary defect, an
achondroplastic or bull-dog type, occurred in the Jersey
herd of the California Experiment Station.
Other
authors have reported different types of this defect, of
which one is due to a dominant gene, lethal when
homozygous and another is due to a simple recessive
gene. Both axial and appendicular skeletal structures
are affected as indicated by a short head, deformed
jaws, a cleft palate and short stumpy legs. The type
reported herein is caused by a monofactorial autosomal
recessive.
The defect is variable, is usually lethal and may affect
both axial and appendicular skeletal structures. Symp-
toms in different cases vary from those having a short,
broad head, legs of slightly reduced length and a
slightly undersized body to those showing such ex
tremely abnormal conditions as a short, broad head,
short ears, very irregular incisor teeth in a very short
and therefore deformed lower jaw so that the incisors
meet the upper jaw opposite the first molars, an
extreme degree of cleft palate, a hard palate developed
only about half an inch on each side and marked
flexion of the anterior pasterns.
It is concluded that the defect is caused by a mono-
factorial autosomal recessive gene, because the observed
incidence fits the expected incidence quite well in each
of three types of matings in this herd. These three
types of matings were: '(1) the mating of a carrier
bull to his own daughters or the daughters of another
carrier bull
; (2) the mating of a carrier bull to
daughters and great granddaughters of carrier sires
and (3) the mating of a carrier bull to daughters, grand
daughters and great granddaughters of carrier sires ,
One bull number 320A, was the sire, grand sire or
great-grand sire of all affected calves borne, although
this bull and one cow, number 344, apparently obtained
the gene from their common sire, number 3,000. It is
unknown, however, whether the mutation occurred with
bull number 3,000 or was handed down to him by or
through one parent.
This type of
achondroplasia
seems to differ from a dominant type found in Dexter
cattle, but seems to resemble the recessive type first
reported in Telemark cattle of Norway. These t wo
latter types do not belong to an allelic series, but
involve two independent loci. [J.N.W.]
Bacteriological methods for the large scale detec-
tion of Mastitis. G. Davis (1942) Vet. Rec. 15, 54
The author emphasises the importance of milk produc-
tion and the prevention of disease, which decrease milk
yield. He lays great stress upon the detection of
mastitis and its early diagnosis in large dairy herds.
The technique which he advocates for its diagnosis and
eradication or control is simple and economic. He has
no confidence in any method other than planting freshly
taken samples in a non-inhibitory medium and picking
off and confirming colonies. Organisms other than Str.
agalactiœ must not be ignored such as Str. dysgulactiœ,
Str. uberis, Str. pyogenes, staphylococci and micro-cocci.
Therefore, it is essential that a non-inhibitory medium
should be used. Heamolysis alone is not a safe method
for the detection of organism carrying mastitis.
He gives in detail the technique to be followed: its
outline is, that, afternoon samples are taken septically
and removed to the laboratory where they are plated on
blood or bromcresol purple lactose chalk agar and
resazurin rennet test performed.
After incubation of
the plates, colonies are transferred to yeast litmus milk,
the cultures incubated and inspected and a catalase test
carried out. The advantages of the method lie in that
centrifuging and the use of blood are unnecessary.*
[W.H.D.]
*A minimum of time, labour and apparatus is required.