In my practice I have never been obliged to make a splenic puncture for the purpose of diagnosis. After repeated careful examinations I believe the exclusion of malaria is justifiable from negative findings.
It is usually only at the beginning of the infection that the parasites are so scanty as to occasion any considerable expense of time and labor. As a rule, they are found in the first preparation. If a microscope is at hand, it is advisable to examine the unstained blood at once; otherwise dried preparations must be made. In regard to the details of the examination and the sources of error, sufficient has been said in the section on Etiology.
If the malarial infection is proved, the next step in the microscopic examination is to determine the kind of parasite and whether the infection is light or severe. This has been described on page 91. A positive conclusion in regard to these details is possible in the great majority of cases.
I have often had the opportunity of p.oving the criteria which we owe especially to Golgi, Marchiafava, and Celli, and I can state that they have scarcely ever left me in the lurch. Only a short time ago I had a man before my class whose assertions in regard to his paroxysms were very confusing. The examination of the blood showed a double quartan, and to the astonishment of my hearers the paroxysms took place promptly as prognosticated. The differential diagnosis between malaria and its sequelae, as well as between it and other acute and chronic diseases, is not infrequently necessary.
Among the fevers coming into consideration are: typhoid fever, sepsis in all its forms (for instance, sepsis in its narrow sense, septic fever from malignant neoplasms, from acute ulcerative endocarditis, from inflammation of the urogenital system, pyelitis, pyelonephritis, angiocholitis, hectic fever of phthisis), all kinds of pyemia, acute gastrointestinal catarrh, yellow fever, Malta fever, relapsing fever, miliary tuberculosis, and filaria disease, as well as other feverish conditions, like the fever of severe anemia, leukemia, malignant lymphoma, and hysteria.
If we add to these the different local syndromes of pernicious and latent fevers, still other diseases arise, requiring a differential diagnosis. We will refrain here from discussing all that might come into consideration, since the most important have been reviewed in the clinical part. Moreover, an examination of the blood is of more service and will lead to a more rapid diagnosis than the most acute reasoning.
The only absolute differential diagnostic characteristic between malaria and other infections is the malarial parasite, and every case not clear is to be diagnosed accordingly.