June 23, 1898] 



NATURE 



175 



Aquatic Hymenopteron. 



It may be of interest to some of your readers to know that, 

 ifter years of unsuccessful search, I have at last bred Prestwichia 

 aqtiatica (Lubbock) from eggs of Notonecta. 



From one single egg there emerged no less than fourteen 

 specimens, one male and thirteen females. This astonishing 

 fact, besides proving that Prestwichia is an ovivorous parasite, 

 beats all previous records of the number bred of allied species ; 

 but this record has since been put into complete shade. On 

 Friday, from another egg, I bred six males and twenty-eight 

 females ; thirty-four parasites from a single egg. 



After this astounding fact we must be prepared for something 

 -trange, now that the life-history of these marvellous ovivorous 

 |i:irasites is being worked out. Fred Enock. 



13 Tufnell Park Road, N. 



"A High Rainbow." 



The " rainbow" described by Mr. Moreland (in your issue of 

 June 16) was evidently of the same character and origin as an 

 inverted arc near the zenith, which occurred in connection with 

 a mock-moon phenomenon at Birmingham, on May 31, 1895. 



An illustrated description of this, by the writer, may be found 

 in Syinons's Meteorological Magazine for September 1895, 

 p. 122. F. J. Allen. 



Mason College, Birmingham, June 17. 



THE ETIOLOGY AND PREVENTION OF 

 MALARIAL FEVER. 



■T^HE study of the causes of intermittent or malarial 

 -^ fevers has received a marked impetus through the 

 discovery by Laveran {Traite des fievres palusires, 1884) 

 of the presence in the blood of the affected persons of 

 definite living bodies belonging to the protozoa. A large 

 amount of important research has been carried on since, 

 concerning these bodies or corpuscles of Laveran, which 

 has yielded not only a clearer understanding of their 

 morphological and biological characters, but has more 

 accurately defined and placed on a firm basis the relation 

 of these protozoa to the different known types of malarial 

 fevers : febris quotidiana, tertiana, quartana — terms 

 denoting the rhythm of the fever paroxysm. The re- 

 searches of Laveran, of Marchiafava and Celli, of Golgi, 

 of Celli and Guarneri, Grassi and Feletti, Councilman, 

 Danilewsky, Mannaberg and others have definitely 

 established that malarial fevers are characterised by and 

 ■due to the presence, within the red blood discs of the 

 patient, of parasites belonging to the group of protozoa 

 known as sporozoa (gregarinida, coccidia and ha^mo- 

 sporidia) ; that is to say, of minute amoeboid corpuscles, 

 measuring not more than a sixth or an eighth or less of 

 the broad diameter of a red blood disc, having entered 

 into a blood disc pass their life cycle intraglobularly, 

 growing in size at the expense of the blood disc, con- 

 suming the latter's substance till of the host nothing but 

 a small mass of black pigment — the remnant of the 

 blood pigment — is left. The final phase in the life-history 

 of this Plasmodium malariie or h;emoplasmodium malari;e 

 is reached when by a process of simultaneous fission its 

 body produces a number of minute oval spores. These 

 becoming free in the blood fluid are carried by the cir- 

 culation into the different internal organs : marrow of 

 bone, brain, and notably the spleen. Here at the proper 

 time each spore germinates into an amoeboid plasmodium, 

 which passes as such into the general circulation, and, 

 having invaded a red blood disc, goes through all the 

 stages of its intraglobular growth and final sporulation. 

 There is a good deal of evidence to show that the phase 

 of sporulation and consequent dissolution of the central 

 part of the parasite, not consumed by the spores them- 

 selves, is actually one of the direct causes of the fever 

 paroxysm ; at any rate, these events coincide with the 

 commencement of the febrile attack. One of the most 

 important amongst the many interesting facts elucidated 



NO. 1495, VOL. 58] 



is this, that the duration of the life cycle of the Plas- 

 modium malariiE stands in a direct ratio to, and deter- 

 mines the rhythm of the consecutive fever attacks in 

 this way : in febris quartana the plasmodium finishes its 

 cycle in seventy-two hours, in febris tertiana in forty-eight 

 hours, and in febris quotidiana and pemiciosa — so 

 common and so virulent in tropical and subtropical 

 regions — the whole process of development is very rapid, 

 the Plasmodia are conspicuously small and very 

 numerous, very active, and sporulation takes place 

 chiefly in the internal viscera, notably the spleen. 



There are other details elucidated, by which the 

 different types of plasmodium malarias can be dis- 

 tinguished from one another ; as by their size, the 

 number of spores produced in each type, the character 

 and intensity of the amoeboid movement, &c., not the 

 least important and fundamental detail being the artificial 

 production by inoculation of the different types of fever : 

 quartana, tertiana or quotidiana, according to whether 

 for the inoculation one or the other or the third definite 

 type of the plasmodium is employed. From all this it 

 seems justifiable to assume that the different types cor- 

 respond, if not to different species, at any rate to different 

 well-defined varieties of the plasmodium malarice. 

 Whether or no these varieties have become "set" and 

 permanent (form -constant), or whether they may in one 

 or another generation, owing to alteration of the con- 

 ditions of host, season, climate or other factors, undergo 

 transition one into the other — as is maintained by 

 some observers — remains to be seen. This, however, 

 has become evident, that by careful microscopic ex- 

 amination of the blood the nature, type and severity of 

 the fever paroxysms can be readily diagnosed and accu- 

 rately determined. This is of particular value in those 

 atypical and irregular forms of malarial fevers, where 

 clinical diagnosis becomes difficult and indefinite, as, for 

 instance, when there exist several generations of plas- 

 inodia in the same affected body, and when these 

 different generations do not start at the same time, and 

 do not finish at the same time their life cycle, as in 

 quartana duplex and triplex. 



Koch, in a recent lecture before the Colonial Society 

 in Berlin, lays justly stress on the importance of sys- 

 tematic examination of the blood by experts, so as to 

 determine the type and character of the parasite, because 

 — and herein lies the chief burden of Koch's remarks — 

 the accurate determination of the type of the plasmodium 

 should guide the treatment of the case. 



It is within common knowledge that the administration 

 of quinine is invaluable in th^ treatment of ague, but it 

 is equally known that in some cases its administration 

 is either of no avail or has proved positively harmful. 



Now, Koch insists on this, that since quinine has the 

 power to arrest and inhibit the growth and development 

 of the Plasmodium, without killing it, the administration 

 of the quinine should be so timed that it is capable of 

 unfolding its effects at the proper phase in the life cycle 

 of the Plasmodium, that is about the time of sporu- 

 lation — immediately before the onset of the fever paro.xysm 

 — or immediately after the germination of the spores 

 into the plasmodia — that is immediately after the onset 

 of the fever paroxysm. These phases can only be deter- 

 mined by accurate and systematic microscopic ex- 

 amination of the blood in each individual case. 



Also in another direction Koch's remarks are of value, 

 viz. in drawing renewed attention to the high probability 

 of the view first expressed by Laveran, then maintained 

 and expressed with ability by Dr. Manson, to the effect that, 

 similarly to what has been proved in Texas fever of cattle 

 for the tick, so also in human malarial fevers the mosquito 

 (or gnat) plays an important part in the transmission and 

 spread of the disease, being in fact the instrument by 

 which natural inoculation is effected. Thus Koch men- 

 tions an island off the coast of German (malarial) East 



