1. Blood samples were collected from Scottish hill sheep ranging
in age from a few weeks to seven years old on four separate occasions
between Jenuary and July* The number of animals sampled and the
dates of sampling were as follows:. January, 11th? 44 sheep; April
5th, 49 sheep; June 7th, 6Z sheep; and July 12th, 37 sheep.
The measurements included packed cell volume, haemoglobin estimations,
erythrocyte and leucocyte counts and differential counts. Values
for mean corpuscular volume and mean corpuscular haemoglobin concentration were calculated, From the results significant variations
in the erythrocytic properties were demonstrated. The sheep under
two years of age were shown to have lower values for packed cell
volume and haemoglobin and hitter mean corpuscular haemoglobin concentration indices than sheep over that age. The erythrocyte
levels, as estimated by packed cell volume and haemoglobin measurements for sheep sampled in January, April and June differed from
each other significantly. The highest levels were recorded in
January, the lowest in April, the values obtained in Jane occupying
an intermediate position* The mean corpuscular haemoglobin concentration for sheep sampled in January was significantly lower than
in sheep sampled in April and June. The significant association
which was shown to exist between packed cell volume and worm burden
in the sheep sampled in January and April suggested that the lower
erythrocyte levels encountered in April were related to the higher
worm burdens found at that time. Standards have been presented in
the form of means and standard error, for the erythrocyte and leucocyte properties In the 194 sheep examined.
e. A technique of marrow biopsy for the sheep by sternal puncture
has been described. From mati\vial obtained by this technique a
description of the histology of the marraa haz been presented.
In the subsequent use of bioptic narrow sampling the examinations
donsisted of differential cell counts and estimation of the incidence
of mitosie among the cells of the marrow, Fran the meats of the
differential cell counts haemomyelograms and eeturation curves have
been constructed. The relative proportions of erythroblastic and
granuloblastio tissue are expressed as a myeloid orythroid ratio.
A scheme for the grading of marrow preparations has been devised to
provide a method of quantitative measurement in the examination of
3. An anaemia was induced in three sheep by bleeding. From an examination of serial samples of marrow obtained by sternal puncturel
it was possible to demonstrate the development of erythroblas tic
hypoplasia in response to the blood loss. The examination of the
peripheral blood included an estimate of regenerative changes, as shown by the presented of immature forms . There was some evidence
that the marrow response to the stimulus of blood loss included a
speeding up of the maturation of the erythroblestic tissue.
4. Blood and bone marrow samples were examined at meekly intervals
for seven weeks from six sheep on measured diets. The bone marrow
was obtained by sternal puncture. The helminth infestation ems maintained at a negligible level. Three of the sheep received a
diet providing full maintenance, and three a diet providing half
maintenance. Be significant difference could be demonstrated in
the range of variation recorded in the two groups. The results
indicate the range of variation likely to be encountered when
successive samples from the same individual sheep are =mined under
artificial conditions of feeding and management.
5. The blood and bone marrow of two sheep were examined at fortnightly intervals from December to June. Two different sheep were
sampled on each occasion and the results of worm burden estimations
carried out after slaughter were available for correlation with
blood and bone marrow findings. The highest levels recorded in the
erythrocytic properties of the peripheral blood were in the eight
sheep sampled up to and including February 8th. From then until
i April 5th there was a gradual fall p the lowest readings occurring at
the latter date. Thereafter there was an abrupt rise, but this
rise was not sufficient to constitute a general return to the levels
recorded prior to February 6th. These chances in the erythrocyte
level w ere accompanied by inverse changes in the worm burden.
There was an increase in the erythroblastic tissue of the marrow of
the sheep sampled frem4nrch 22nd to iay 17th as compared with the
marrow of the sheep sampled before and after this period. The,
influence of the helminth burden and nutrition on the erythron is
discussed. Evidence is advanced to show that the reduction in the
erythrocyte levels observed in Febryary, March, and early April was
related to the increase in worm burden which occurred at this time.
The relative paucity of erythroblastic tissue in the marrow
considered to have facilitated this effect. The increase in erythroblastic tissues which coincided with the onset of weather conditions
favourable to the growth of pasture assisted the return of erythrocyte
values to higher levels.
6. An examination of the blood and bone marrow was oarrfied out
on fifteen lambs in a debilitated condition following an attack of
the malignant form of contagious pustular dermatitis. It was
possible to show that the anaemia found to exist in a timber of the
lambs was associated with sane dome of erythroblastïc hypoplasia.
7. A study of the blood and bone marrow was carried out in six
cachetic sheep which showed symptoms of anaemia. In five of the
sheep varying degrees of erythrobtastic hypopla is ,ere demonstrated,
and in, the sixth, e state of hyperplasia of the crythroid tissue
was shown to exist.