For the purposes of this study I have examined
the blood in thirty cases of active, uncomplicated
rickets in children between the ages of 13 months
and three years. One case of a child aged 6.5 years
I have included because I felt justified in classing it as a case of pure active rickets. The majority of these cases were under the care of the physicians to the Northern Hospital, Manchester, to whom
I am much indebted for the opportunity of examining
them. The remainder came under my observation in
the Out- patient Department of the Oldham Infirmary.
My examinations were timed so as to exclude all
avoidable sources of error. In every case the
blood was taken at least three hours after a meal
(in order to exclude digestive lymphocytosis), and
at about the same time of day. The corpuscle enumeration was made by means of the Thoma -Zeiss apparatus, using a dilution of 1 in 200 and Toisson's
solution as a diluting medium. The red cells deposited on one square millimetre - frequently those
on two square millimetres - and the white corpuscles
distributed over eighteen square millimetres were
counted. This operation was made possible by the
use of the Elzholz ruling on the Thoma-Zeiss slide,
a device which considerably shortens an otherwise
lengthy operation. The haemoglobin was estimated
with a von Fleischl instrument with which, in my
opinion, a greater degree of accuracy is possible
than by the use of the instrument of Gowers. In
every instance Tallgvist's "Haemoglobin Scale" was
used in addition and confirmed the results obtained
by the Fleischl apparatus to within 5 per cent.
The specific gravity of the blood was estimated by
the method of Hammerschlag (chloroform-benzol mixture), and after a little practice with the blood of
normal individuals I was able to obtain readings involving a possible error of not more than 1 per cent.
At the same time a number of blood films were made
on slides, and the best of these were suitably stained and examined under a 1 /12th inch objective.
Louis Jenner's stain was found to yield the most
uniform results, and in some cases Leishman's modification of Romanowski's stain was used with equally
satisfactory results. A differential count was
made of 1000 leucocytes, and in the majority of
cases the figures were confirmed by a second census.
The classification recommended by Ehrlich was adopted. (Under the term 'lymphocyte' I include both
small and large lymphocytes, while the term 'large
mononuclear' covers "transitional" cells and large
"hyaline" mononuclear cells.) The characters of
the red corpuscles were noted at the same time as
the leucocyte census was made, abnormal forms were
counted, and the estimation per cubic millimetre
The cases have been divided roughly into three
groups according to their clinical type: those showing a mild degree of rickets, those in which the
process is more severe but in which there is no
splenic enlargement, and those in which there is
splenic tumour. The first group comprises 15 cases,'
the second 11, and the third 4. I would have wished for a larger number of cases with enlarged spleen,1
but the comparative rarity of these cases in pure
rickets seems to have been even more marked during
the time available for my study, and cases with
great splenic enlargement unfortunately did not come
under my observation.