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2 Great Britain, much more is it so of Tropical Disease, where we see such variations from the so-called normal course of a fever that we almost at times feel unjustified in describing a normal course. Again, whilst at home blood examination is seldom diagnostic, in several important tropical diseases it is absolutely diagnostic, and this list will probably increase in proportion to the attention devoted to this subject. As examples of disease where the fever chart is sometimes most atypical, we might quote as striking examples, typhoid in the tropics and malaria; and of diseases where blood examination may be absolutely diagnostic we have malaria, trypanosomiasis, filariasis, kala-azar, relapsing fever, and possibly a few others—as, for instance, the septicsemic form of plague when a culture is obtained.

The correct diagnosis of a disease may often mean the saving of a patient's life, or certainly a prolongation of his days, and so we are much to blame if we lightly lay aside this method of investigation, which, it may be, would prove the key to the riddle.

We cannot, in a paper such as this, enter into the full technique of blood examination;