September, 1950] G. L. SHARMA AND C. SEETHARAMAN 205
from the sternal area which is then cleaned with absolute alcohol and allowed to
dry. The operator then feels for the heart beat with the fingers of his left hand.
The beat is almost invariably located to be most prominent at the space between
the sternum and the root of its posterior lateral process. This point is generally
about a couple of inches on the line drawn backwards and upwards from the point
of the sternum. A wide bore needle fitted to a 5 c.c. syringe is gently introduced
at this point, downwards, forwards and a little to the right. When the point of
the needle touches the heart the beat is prominently felt by the operator and the
needle is then carefully pushed further. The blood starts flowing into the syringe
on the application of a gentle pull to the piston. Usually 3 c.c. of blood was drawn
at each puncture. The needle is then carefully withdrawn and immediately dis-
connected from the syringe and the blood run along the side of the test tube contain-
ing the required quantity of the anti-coagulant. The tube is shaken for about
two minutes to ensure a thorough mixing of the oxalate powder with the blood.
The examination of the blood was immediately started and the procedure
adopted was : (1) preparing smears, (2) estimation of the percentage of haemo-
globin, (3) estimation of corpuscular volume, (4) determining total erythrocyte
and leucocyte counts and (5) examining the smears for differential count. It
generally took about four hours to go through the whole procedure.
Blood from each fowl was examined on two consecutive days and then the bird
was infected with virulent Ranikhet disease virus. Birds so treated were generally
found to develop clinical symptoms of the disease in about 72 hours and invariably
succumbed to it after 96 to 120 hours. Examination of the blood for the study of
changes in the disease, was, therefore, conducted on the third and fourth day after
infection.
Technique
(a) Examination of smears. Uniformly thin films were made. In order to
take the same quantity of blood for making uniform smears, a platinum loop with
a diameter of 2 mm. was employed throughout this work. Smears were stained
by Giemsa's method. A combination of ' edge ' and ' cross section ' methods
was employed for differential white blood cell count and the number of leucocytes
counted in each examination was in no case less than 200.
(b) Haemoglobin determination. Haemoglobin percentage was estimated by
Sahli's haemoglobinometer and the reading so obtained corrected by Dukes and
Schwart's formula given by Olson [1935].
(c) Total erythrocyte and leucocyte counts. For total erythrocyte
and leucocyte counts the stage with Neuber's ruling was used while Toison's fluid
served as the diluent. Red blood pipette was employed in collecting the blood.
(d) Corpuscular volume and the time required for the complete sedimentation of
corpuscles. Scrupulously clean Wintrobes haematocrit tubes (length 11 cm. ;
bore 2.5 mm. graduated with a centimetre and millimetre scale 10 cm. in length)
were used. Two such tubes filled with blood up to the mark ' 10 ' were centrifuged
at a speed of about 3000 rounds per minute. At first the tubes were spun for ten
minutes and subsequently for periods of five minutes each. After each interval
the centrifuge machine was switched off and allowed to come to a standstill by itself
and the corpuscular volume noted. When two consecutive readings were constant
K 2