joo THE EAR
held up in the pulmonary capillaries, but if they are small they can pass
through and reach the bones, joints or subcutaneous tissues.
DIAGNOSIS. The conditions with which sinus thrombosis is most likely to
be confused are malaria, typhoid fever, bronchopneumonia and erysipelas.
The diagnosis of sinus thrombosis is suggested by the occurrence of rigors
in the course of a middle ear suppuration; it is more difficult if the condition
is complicated by the presence of meningitis or brain abscess. Sinus throm-
bosis may occur in cases where middle ear suppuration is not suspected;
Fig. 190. Vertical coronal section through middle and inner ear showing route of infection in a case of
primary septic thrombosis of the jugular bulb. 1, Smooth part of superior vertical canal; 2, Ampulla of
superior canal; 3, External meatus; 4, Tympanic cavity; 5, Pus in lower part of tympanum; 6, Thickened
lining membrane of jugular bulb; 7, Laminated clot in the bulb; 8, Point at which infection passed
from tympanum to bulb; 9, AmpuUary end of posterior vertical canal; 10, Crus commune.
this error is not likely to arise If the condition of the ears is ascertained. A
high leucocyte count with a high percentage of polymorphonuclear leuco-
cytes (80-95 per cent) shows a severe infection. Repeated examinations of
the blood are of more value than single tests in regard to prognosis, but it
cannot be said that the leucocyte count serves to distinguish cases of venous
infection from those of extradural abscess or septic meningitis. As a rule,
however, the count is lower in brain abscess than in the other intracranial
complications. Blood cultures taken during the phase of rising temperature