682 



NATURE 



[May 27, 1922 



to malaria, he says : " The man who actually ' dis- 

 covered ' the fact of the carriage of malaria germs by a 

 mosquito and the particular species {Anopheles maculi- 

 pennis) so concerned, as well as important facts as to the 

 multiplication of the malarial parasite in the gnat's 

 body, is Sir Ronald Ross." This short statement 

 includes several mistakes. In the first place. 

 Anopheles maculipennis is not the only anopheline 

 concerned in the transmission of malaria, because 

 several species belonging to the genera Anopheles, 

 Myzomyia, Pyretophorus, Myzorhynchus and Cellia 

 play an active part in the transmission of the inter- 

 mittent fevers, within their respective habitats. 

 Then again. Anopheles maculipennis was unknown 

 to Ross in India for the simple reason that it is 

 not to be found anywhere within the Indian triangle. 

 Anopheles maculipennis is a Holarctic species ranging 

 over North America and throughout Europe and 

 extending round, the shores of the Mediterranean 

 Sea and its islands, but otherwise absent from both 

 the Oriental and Ethiopian regions. 



Sir Ray Lankester states that Prof. Laveran, the 

 discoverer of the malaria parasites of man, had 

 already previously suggested mosquitoes as the 

 carriers of paludism. I can adduce much older 

 evidence to prove that in malarial stations the 

 natives long suspected the mosquito as the probable 

 cause of infection, just as the tick was suspected of 

 being the carrier of relapsing fever and the body 

 louse the vector of typhus, because the name of 

 the dread " Fever-fly " is inscribed in cuneiform 

 characters on a Babylonian clay tablet of thousands 

 of years ago, now preserved in the British Museum. 

 But Sir Ray Lankester ignores Manson's brilliant 

 interpretation of the " flagellating " malarial parasite, 

 looked upon by the Italians as a form of degeneration ; 

 by Manson as the prelude to a further all-important 

 developmental stage outside the body of man. He 

 overlooks the fact that Ross's investigations were 

 inspired by Manson, and that Ross was all along 

 instructed, aided, and supported by Manson. I need 

 but quote Ross's own words in the paper he sent 

 to the French Academy of Medicine, January 24, 

 1899 : " Pour eviter tout commentaire erroni, qu'il me 

 soit permis de declarer id que mes tvavaux ont ete 

 entierement dirigis par Manson, et que j'ai eu I'assis- 

 tance de ses conseils et de son influence A toute occasion." 

 During the whole period of Ross's work in India, I 

 was almost daily at Manson's house, where I had the 

 privilege and good fortune of being able to follow 

 step by step the unfolding of one of the most 

 wonderful chapters of tropical medicine. I was 

 allowed to read the correspondence, examine the 

 specimens sent by Ross to Manson, and discuss every 

 detail. I do not wish to minimise in anyway the 

 importance of Ross's work. Humanity and science 

 are greatly indebted to Ross for his splendid researches 

 and no one appreciated this more than Manson. but 

 all the world knows that Manson was the man at 

 the helm ; Ross himself has stated it quite frankly 

 and honourably in his writings. 



It was Manson who first clearly grasped the 

 problem, it was Manson who planned the modus 

 operandi, it was Manson who chose the man who 

 should carry out his ideas and do the work, and, 

 when failure threatened, as in the case of the Italians, 

 when they attempted to solve the problem, it was 

 again Manson who saved the situation, by suggesting 

 that the researches be continued with the Plasmodium 

 parasites of passerine birds. Indeed, the hfe cycle 

 studied and unravelled by Ross was that of Plas- 

 modium danilewskyi, a blood parasite of sparrows 

 and not that of any of the malarial parasites of man. 

 It was in Italy, by Profs. Grassi, Bignami, and 



NO. 2743, VOL. 109] 



Bastianelli, that it was actually proved that the 

 malaria parasites of man go through exactly similar 

 transformations and migrations as those of Plasmodium 

 danilewskyi ; not, however, in any of the Culicinae, 

 as Ross had proved for the bird parasites, but in a 

 different subfamily of mosquitoes, the Anophelinae. 

 Finally, the experiments carried out by Manson in 

 London and by Dr. Low and myself in the Roman 

 Campagna, in 1900, put the last brick in the structure 

 of proof and were especially important in proving that, 

 under natural conditions, the intermittent fevers 

 cannot be contracted in any other way than through 

 the stab of AnopheUne mosquitoes. However, it is 

 only right to say that Ross's experiments were 

 undertaken at Manson's request, for the sole purpose 

 of elucidating the etiology of human malaria, that 

 Ross began by using the Plasmodium parasites of 

 man, and that the first mosquitoes he infected and 

 examined were " dappled-winged " mosquitoes, that 

 is to say, in all probabihty, Anopheline mosquitoes. 

 Great discoveries are seldom made by a single man. 

 Ross would never have done this work had he not 

 come across Manson, and probably Manson might 

 have had long to wait for the establishment of his 

 theory had he not found Ross. 



With regard to sleeping sickness. Sir Ray Lankester 

 is no better informed. Sir David Bruce did certainly 

 prove that " nagana," the horse disease of Africa, 

 is caused by the same kind of parasite — a trypanosome 

 — discovered by Evans, eleven years previously, in 

 " surra," the horse disease of India, and he repeated 

 very fully the experiments previously made by Dr. 

 David Livingstone and by others to ascertain whether 

 the African natives were right in suspecting the 

 tsetse flies as carriers of the infection, but, un- 

 fortunately, Bruce gave wrong interpretations to. 

 his own experiments and to those of others, contend- 

 ing that the fly acted merely as a passive carrier, 

 " just as a vaccinating needle " — these are his very 

 words. 



It was Prof. Aldo Castellani who first demonstrated 

 the true causative agent of sleeping sickness — a 

 trypanosome which he found not only in the blood, 

 but also, and chiefly, in the cerebro-spinal fluid 

 of sleeping-sickness patients. At the same time, 

 Prof. E. Brumpt of Paris and I, independently, 

 simultaneously, and some months before the publica- 

 tion of Bruce 's work, incriminated a tsetse fly as the 

 carrier of sleeping sickness. Prof. Brumpt suggested 

 Glossina morsitans as the probable vector, basing his 

 belief partly on Castellani's discovery and partly 

 on his own extended field work in the French Congo. 

 I incriminated the dusky tsetse fly {Glossina palpalis), 

 basing my opinion on a careful study of the pecuhar 

 topographical distribution and other striking epi- 

 demiological features of the disease, on analogy with 

 the better known epidemiology of nagana, and on 

 the bionomics and distribution of the then known 

 species of tsetse flies. At the International Con- 

 ference on Sleeping Sickness (London, 1907) and at 

 several meetings of the British Medical Association, 

 I endeavoured to prove that the " sexual " dimor- 

 phism noticed first by me in the trypanosomes of 

 sleeping sickness (specimens forwarded by Dr. Low 

 to the School of Tropical Medicine) and a critical study 

 of Bruce 's experiments on both nagana and sleeping 

 sickness showed that the respective trypanosomes go 

 through a necessary cycle of development (sporogony) 

 within the body of their definitive insect-hosts, 

 analogous to that of malaria parasites in the body 

 of mosquitoes. Six years later (1909) Klein's careful 

 researches in Africa fully proved the justice of my 

 interpretations. 



Louis W. Sambon. 



