at the present time. The important point is that the result of the segmentation of the adult parasites contained in the red corpuscles is the formation of a large number of spore-like bodies, which are set free by the disintegration of the remains of the blood corpuscles and which constitute a new brood of reproductive elements, which in their turn invade healthy blood corpuscles and effect their destruction. This cycle of development, without doubt, accounts for the periodicity of the characteristic febrile paroxysms; and, as stated, the different varieties complete their cycle of development in different periods of time, thus accounting for the recurrence of the paroxysms at intervals of forty-eight hours, in one type of fever and of three days in another type. When a daily paroxysm occurs, this is believed to be due to the alternate development of two groups of parasites of the tertian variety, as it has not been possible to distinguish the parasite found in the blood of persons suffering from a quotidian form of intermittent fever from that of the tertian form. Very often, also, the daily paroxysm occurs on succeeding days at a different hour, while the paroxysm every alternate day is at the same hour, a fact which sustains the view that we have to deal, in such cases, with two broods of the tertian parasite which mature on alternate days. In other cases there may be two distinct paroxysms on the same day, and none on the following day, indicating the presence of two broods of tertian parasites maturing at different hours every second day.
Manson, in his work on tropical diseases, recently published, accounts for the febrile paroxysm as follows:
"In all malarial attacks this periodicity tends to become, and in most attacks actually is, quotidian, tertian, or quartan in type. If we study the parasites associated with these various types we find that they, too, as has been fully described already, have a corresponding periodicity. We have also seen that the commencement of the fever in each case corresponds with the breaking up of the sporulating form of the parasite concerned. This last is an important point; for, doubtless, when this breaking up takes place, besides the pigment set free, other residual matters—not so striking optically, it is true, as the pigment, but none the less real—probably are liberated; a hæmoglobin solvent, for example, as I have suggested. Whether it be this hæmoglobin solvent, or whether it be some other substance, which is the pyrogenetic agent, I believe that some toxin, hitherto enclosed in the body of the parasite, or in the infected corpuscle, escapes into the blood at the moment of sporulation.
"The periodicity of the clinical phenomena is accounted for by the periodicity of the parasite. How are we to account for the periodicity of the parasite? It is true that it has a life of twenty-four hours, or of a multiple of twenty-four hours; but why should the individual parasites of the countless swarm all conspire to mature at or about the same time? That they do so—not perhaps exactly at the same moment, but within a very short time of each other—is a fact, and it is one which can be easily demonstrated. If we wish to see the sporulating forms of the Plasmodium in a pure intermittent, it is practically useless to look for them in the blood during the latter stages of fever, or during the interval, or
