It was the custom of the old writers to differentiate among the malarial fevers pernicious forms. This custom has been continued, and though it no longer has the justification that it had, for instance, in Torti's time, it will probably be prolonged for some time into the future.
By the expression "pernicious fever" we understand one directly threatening to life. This must not be the result of the occurrence of a second disease,-in other words, a complication,-but the malarial fever itself must be responsible for the dangerous symptoms.
We search pathology in vain for an analogy. As far as I know there is no other disease, though it runs its course sometimes smoothly, and without prognostic danger, again under the severest and most threatening symptoms, for which a division into benign and pernicious has been made. If we were to follow out this division, we should speak of a benign typhoid fever when the disease was mild, of a pernicious typhoid fever when, in its evolution, dangerous symptoms arose. There would be, in addition, an endless series of subdivisions, depending on whether the dangerous symptom proceeded from one or another organ. The same scheme might be carried out also for all other diseases that terminate not necessarily fatally or in recovery. Difficulties would naturally not be wanting, for not all physicians would be unanimous as to what symptoms should be considered pernicious.
There is nothing further from my mind than the thought of reproaching the old writers, of whom especially Torti stands out immortal for introducing the notion of pernicious fevers. If we think back to that time when the most primitive pathologico ana tomic and etiologic knowledge was wanting, we see at once that besides the symptoms apparent to the senses, it was the severity of the symptoms which acted as the most important basis in the classification of diseases. With the further development of knowledge, for which we must thank the genius and diligence of generations, our foundation has been broadened. The occasional severity of a disease, though it must be taken into consideration for the sake of the patient, is evidently useless as the basis of a scientific classification It is possible that the future may so solve the question that from the individual susceptibility and the toxicity of the parasite the appearance or non appearance of dangerous symptoms will be prognosticated with astronomic certainty. A beginning has already been made in the recognition of the facts that the parasites of the first, no matter how strong or numerous the generations, scarcely ever produce pernicious fever, and that perniciousness is almost exclusively confined to the infections caused by parasites of the second group. Further than this we cannot go at the present moment, and we must take the group of infections caused by crescent forming parasites as a whole and say that they are sometimes mild, sometimes severe, under circumstances even fatal, as is the case in many other infectious diseases.
Although we have established the fact that a classification on the basis of the severity of the symptoms is not scientifically justified, we must add that the most thorough analysis of the severe symptoms is a primary essential.
For this reason we shall first consider the question: Of what kind are the pernicious symptoms ? Even the answer to this primitive question raises difficulties, since there are very few symptoms which, without argument, can be looked on as dangerous to life. I will say at once, in order not to pick the matter all to pieces, that we will consider the word "pernicious" in a broad rather than a narrow sense, and include under it not only the symptoms directly threatening life, but all that may be considered dangerous or even severe.
The pernicious symptoms may be associated with the nervous system, the vascular system, the gastro intestinal tract, the genitourinary system, the spleen, and, in rare cases, even other organs. In a large number of cases it is the whole organism that produces the general impression of a status perniciosus without any definite local symptoms, though again there are cases in which several organs, as, for instance, the nervous system and the intestinal tract, either simultaneously or alternately, present the pernicious symptoms. It is especially this last that makes a division of these forms so difficult from a clinical standpoint; yet certain groups of symptoms are repeated so frequently that a separation of these into types is clinically justified, especially since we are in a position to handle them in no other way.
As regards the frequency of pernicious fever, statistics are almost unavailable, for the reason that every physician and every malarial region has a different conception of the word "pernicious." Still there is no doubt that in certain " severe malarial regions " more pernicious cases, sensu strictiori, occur than in others, even when the latter show just as frequent infection with crescent forming parasites. It is, moreover, generally recognized that the number of pernicious fevers varies in different years.
Colin states that in 1864 the French Army of Occupation at Rome showed a proportion of pernicious to ordinary fevers of 1: 25. In the same year the civil population of Rome showed a proportion of 1: 20. Laveran observed in Constantine (Algeria) a proportion of not more than 1: 35-40. According to Galvagno, there were treated in the Clinical Hospital in Catania, in the years 1893 to 1895, 1022 cases of malaria , of which only four were pernicious, while in Kam erun, Albert Plehn observed a proportion of 1: 8.5; Frederic Plehn, 1: 11 or 12. Schellong, at Finschhafen (Kaiser William's Land), had 7.3 per cent, mortality; Martin, in Deli (Sumatra), had, on a tobacco plantation worked by Chinamen, over 80 deaths among 200 laborers.