Gr. H. F. Nuttall 
281 
apparently horses and dogs, man being unaffected. Once infective 
G. morsitans remains infective doubtless as long as it lives. Tested 
under experimental conditions, this fly has proved infective 88 days 
after first imbibing the trypanosome. Through experiment with flies 
bred in cajjtivity and consequent!}' “ clean ” to start with, it has been 
shown that 0. palpalis may also transmit T. brucei. As in T. gamhiense 
and T. rhodesiense, it has been found that this fly does not become 
infective until about the 18th day and remains infective up to the 
66th day and no doubt considerably longer. 
So7ne other Glossina-G-ansmitted Trypanosome Infections. 
Trypanosoma dimorphon and T. pecaudi also appear in the salivary 
glands when the flies become infective. These trypanosomes are 
transmitted by G. tachinoides and G. longipalpis ; T. dimorphon may 
also be conveyed by G. morsitans. 
T. cazalhoui is transmitted by several species of Glossina (^morsitans, 
palpalis, longipalpis and tachinoides)^. When laboratory-bred flies are 
allowed to feed upon blood containing this trypanosome, 20-70'^jo of 
them become infected. Glossina palpalis becomes infective after 6-7 
days^ or after 17 days®, moi'sitans on the ninth day® or on the 21st to 
30th day®. After the fly feeds the parasites assume a crithidia-like form 
(48 hours) and remain attached by the flagellar end to the labrum or 
hypopharynx, the infective forms resembling trypanosomes remain con¬ 
fined to the region of the fiy s proboscis. Infection has been produced by 
inoculation of animals with the proboscides of infected flies. The flies 
presumably remain infective for life, palpalis having been found to 
convey the trypanosome to susceptible animals 75 days after having 
infected itself. 
In all the species of trypanosomes which have been enumerated 
{garnbiense, rhodesiense, brucei, dimorphon, pecaudi and cazalboui) we 
have no evidence that the parasites are transmitted to the offspring of 
the flies which serve as vectors. In all cases the trypanosomes may 
occasionally be transmitted mechanically by the fly for a brief period 
after it has imbibed infective blood, and this is followed by a more 
or less lengthy period during which the fly is uninfective. Then, 
coincident with the appearance of parasites resembling the blood forms 
of the trypanosomes in the salivary glands or proboscis {T. cazalboui), 
1 T. vivax is regarded as identical with T. cazalhoui. 
- According to French observers. 
® According to British observers working in a different locality with T. vivax. 
