2 
REPORT OF THE MALARTA EXPEDITFON. 
In 1897 MacCallum had already supplied an important fact in the life-history of the 
group by demonstrating the sexual nature of certain forms (gametocytes) of the organisms [9]. 
At the end of 1898, Koch and Grassi, Bignami and Bastianelli, almost simultaneously 
confirmed these observations. It was found that in Italy, as in India, the human species develop 
in gnats of the genus Anopheles ; and the Italian observers finally succeeded in infecting healthy 
human beings by the bite of previously infected insects of this kind [10, 11]. 
The results of these investigations have been accepted by Ray Lankester, Laveran, 
Manson, MetchnikofF, and others ; and a full history and bibliography of the subject has been 
published by Nuttall [12]. 
To sum up ; although some points of importance still require investigation, it has been 
shown that certain species of gnats are definitive hosts of the Haemamcebidae ; that the parasites 
are conveyed from diseased to healthy vertebrates (intermediary hosts) by these insects ; and 
that the definitive hosts of the human parasites are certain species of Anopheles [Section r.]. 
2. Objects of the Expedition. — As soon as these facts were ascertained it became 
necessary to enquire whether the discovery could not be turned to practical account for the better 
prevention of malarial fever. The question was theoretically examined at length by one of us 
in February [13], and again in May, 1899 [14]. From an early stage in his investigations in 
India lie had noted that, so far as his studies then went, gnats of the genus Anopheles sometimes 
appeared to breed only in comparatively small and isolated pools of water — a fact which 
suggested that in some localities it may be possible to exterminate them without great difficulty. 
Unfortunately his observations had not been exhaustive enough to enable him to speak with 
confidence on the point ; while other students of the subject had not given it sufficient attention. 
Hence the Liverpool School of Tropical Diseases undertook to open a special investigation 
of the question ; and despatched an expedition consisting of ourselves to the West Coast of Africa 
for the purpose. Our objects were as follows : — 
(i.) To find one or more species of insects hospitable to the human Haemamcebidae on 
the West Coast of Africa. 
(2.) To study the bionomics of these insects with a view to suggesting better modes of 
prevention of malarial fever than those hitherto known to us. 
It was not proposed that the expedition should remain in Africa for more than a few 
weeks ; and it will therefore be understood that, owing to the short time at our disposal, we were 
obliged to limit our investigations strictly to the matter in hand. 
3. History of the Expedition. — Sierra Leone was selected for the field of the first 
operations. 
The expedition primarily consisted of (i) Major R. Ross, Lecturer in Tropical Medicine, 
University College, Liverpool ; (2) Dr. H. E. Annett, Demonstrator in Tropical Pathology, 
Liverpool School of Tropical Diseases ; and (3) E. E. Austen, Esq., Zoological Department, 
Britisli Museum. 
