12 
REPORT OF THE MALARIA EXPEDITFON. 
No. 92. Very numerous large zygotes, probably H. malaria. 
„ 99. Several empty capsules. Numerous blasts in blood, and a few in cells of salivary 
gland — none in ducts. 
„ 108. One nearly mature zygote. 
It is possible that the parasites may have been overlooked in some of the gnats examined. 
That a larger percentage of the gnats should not have been infected, and that more zygotes should 
not have been found in them, was to be expected from the old nature of most of the fever cases 
among the men [^paragraph Iff]^ and from the constant use of quinine by the medical officer. 
The facts obtained, however, removed all possibility of doubt as to A. costalis being 
hospitable to the human parasites ; and it was no longer necessary to undertake formal feeding 
experiments. Indeed the condition of things found in the Wilberforce Barracks amounted to an 
experiment of this kind being performed by nature herself under our eyes. This was the more 
fortunate as we experienced great difficulties in the way of actually feeding gnats on infected 
persons in a satisfactory manner. Nevertheless a few such experiments were performed. 
On the 17th August, five small Anopheles [A.funestus) caught at Kissy, were fed on a case 
containing a few H. malarice. The insects had been naturally fertilized and fed when caught, 
but had been kept for some days until they had digested their meal and had laid their eggs. They 
were then fed again in test-tubes on the case referred to, and were kept for another two days before 
being examined. Two yielded bad dissections, and one died before its meal of blood was digested. 
The fourth was negative. The fifth was dissected on the 19th, and was found to contain three 
very young zygotes with pigment identical with that of H. malaria. 
A few days later, one large Anophele [A. costalis)^ also caught by hand and previously 
naturally fertilized, fed, and kept in the same manner as the preceding, was re-fed on the same 
case. Two days afterwards several young zygotes containing the melanin of H. malaria were 
found in it. 
In both these successful experiments the insects concerned belonged to large batches of 
Anopheles procured from a building where there was no fever ; and numbers of insects of both 
batches had been examined and found free from parasites. Judging from this fact, and from the 
size of the zygotes found, there could be no doubt that the latter had been derived from the case of 
H. ynalaria. It should be carefully noted, however, that both these insects had evidently been 
fertilized before they had been caught, and had indeed each laid a batch of eggs before the 
experiments. 
The military medical authorities now put a stop to our feeding any gnats, except those bred 
from the larva, on their cases. As it took us some weeks to obtain Anopheles in this manner, and 
as we could then only feed the insects in a very unnatural manner, that is, in tubes, our experi- 
ments in this line were practically arrested. 
Altogether eighteen Anopheles., mostly of the large variety, all of them bred from the larva, 
and some of them bred frorn the eggs of Anopheles caught at Wilberforce, were applied in test-tubes 
to the skin of patients containing a few H. prcecox (crescents) and H. malaria, and taking quinine — 
no better cases being available. Being isolated in test-tubes when fed, none of these insects 
