MALARIAL PARASITES 193 
here there are two generations of the same Plasmodium, which, developing 
alternately, produce an attack every 24 hours. The double and the triple 
quartan are rare forms; the first is marked by two successive days of fever, fol- 
lowed by a day of repose, while in the second the attacks are daily. The explana- 
tion is the same, the presence in the same individual of two or three generations 
of Plasmodium malaria which alternately undergo schizogony. 
In acute cases of malignant tertian the attacks are prolonged and another 
attack begins before the previous one has ended; such attacks are called sub- 
intrant, There are cases in which a continuous fever appears. As there are 
diverse generations of the parasite, whenever any one of them enters into schi- 
zogony this is indicated by a fever-paroxysm, generally preceded by a chill which 
coincides exactly with the schizogony. The initial chill can be absent in malig- 
nant tertian fever; it is, however, always present in benign tertian and in 
quartan fever. 
When more than one species of Plasmodium is found in the blood this associa- 
tion is called a mixed infection. These are most frequently produced by the 
parasites of benign tertian and malignant tertian fevers and it is very rarely 
that one of these forms has been reported as associated with the quartan parasite. 
In these cases not only does each Plasmodium develop in the most complete 
independence, without the development of one affecting that of the other, but 
also the two species can grow and develop within the same blood-corpuscle with- 
out interfering with each other. The same thing happens with like or unlike 
elements of the same species. For example one corpuscle can be infested by 
various schizonts, each one of which goes through its evolution without disturb- 
ing the others ; or, the same may occur with schizont and gamete, male or female, 
when they happen to be found together in the same corpuscle. 
The mixed infections have contributed much to furnish arguments for the 
unicists who believed in the existence of only a single species of Plasmodium and 
that this was capable of transforming into varieties, according to temperature, 
the transmitting species, the climate, ete. Kinoshita has demonstrated that from 
the odcyst onward the species of parasites can be differentiated. These differ- 
ences become more marked, both morphologically and biologically, in the differ- 
ent stages of schizogonic development and moreover produce different organic 
reactions. The specific identity of all the parasites is a point now disposed of. 
Few still defend this extravagance and among these there is only one of uni- 
versal renown. 
Another hypothesis, formulated by some authors, is in a similar position. 
This is the hypothesis of the possible transmission to man of the Plasmodium of 
monkeys, and, more startling, of other similar parasites of various animals. 
Some points in relation to the malarial parasites still await future research 
to better elucidate them. The hereditary transmission of the sporozoit to the 
egg of the mosquito is a possibility indicated by Schaudinn. This investigator 
also believed in a differentiation of the sporozoits into males, females and un- 
differentiated. The belief in the possibility that another cycle may occur in the 
mosquito, different from that already known and perhaps more rapid, can not 
