The blood pressure in those cases in which cyanosis was observed was invariably low. This seemed to be due to the infection, for in several private patients not belonging to this group of patients with previously known high blood pressures the blood pressure was observed as much lower throughout the course of the infection.
The peculiar behavior of the white blood corpuscles will be discussed more fully in another paper of this series. Our remarks will deal more particularly with the clinical observations and interpretations. The leucocytes fell below the normal from the very onset of the disease; they varied very little regardless of great changes in temperature; they did not always increase, or if they did increase at all it was comparatively little, even in an extensive invasion of the lungs or in severe complications. Concerning the leucopenia we have no explanation to suggest, save that it is a clinical characteristic of the disease. Our first thought was that the infection came on so suddenly and profoundly there was no time for a leucocyte reaction. But when we recall other diseases associated with a leucopenia, notably typhoid fever, which does not come on with such suddenness, our explanation for the leucopenia of influenza does not seem to hold. The leucopenia must be simply a peculiar toxic blood reaction characteristic of the Pfeiffer bacillus invasion. Such an explanation has long been accepted in the Eberth bacillus infection.
A condition which was frequently noted by the patient was an indescribable weakness and prostration which appeared early, sometimes before any other symptoms were noted or before any elevation of temperature. The young soldier was in apparent perfect condition when he arose in the early morning. During the “setting up” exercises he did not feel so fit, and a few hours later appeared extremely weak. When his condition was called to the attention of the medical officers he was found to have a slight elevation of temperature and was sent to his bed.
In former epidemics, as also in this one, marked prostration was recognized as coming at the height of the disease and remaining persistently during convalescence. But it does not seem to be recorded as among the first symptoms.