FILARIA TRANSMITTERS 315 
Finally, the last step in the process of filarial infection remained obscure 
until 1908, when it was made known by Fiilleborn. This is the mode of entry of 
the worms into the body of the vertebrate host. It was supposed that the filariz 
gained access to the body directly through the wound inflicted by the mosquito 
and while it is engaged in sucking. This Fiilleborn disproved, both by careful 
direct observation and by long series of preparations of skin with the parasites 
in the act of penetrating. 
“ According to the suppositions of most authors the place at which the filarie 
enter the skin is through the channel made by the puncture of the mosquito. 
At this point the entrance of the filarix can not well take place during the process 
of sucking, for between and besides the piercing sete the filarie can not pene- 
trate because the stylets form a compact bundle which tightly plugs the channel 
of the puncture. It is possible that they sometimes choose this prepared passage 
after the mosquito has taken flight, for during the act of sucking, which only 
lasts a very short time, it appears that, as a rule, they do not enter the skin at 
all; in my experiments I only found them in the skin when there had been an 
interval, not too short, between the act of sucking and the cutting away of the 
skin (involving the killing of the filarie). But that the filarie certainly do 
not need the perforation made by the mosquito to get into the depths of the 
skin is apparent from the fact that I also found them in the skin when no mos- 
quito puncture had taken place and they were simply placed upon the skin of 
the experimental animals; they evidently behave similarly to the Ankylostoma 
larve, a supposition which Eysell has also expressed.” 
MOSQUITOES THAT TRANSMIT FILARIASIS. 
The full development of the filarial larvae, and consequently their transmis- 
sion, can only take place with certain species of mosquitoes. In others the 
embryos are either digested or eliminated through the digestive tract, or they 
undergo a partial metamorphosis and then die. 
In the case of Filaria bancrofti a number of species of mosquitoes are effective 
hosts, but in an unequal degree. The most important transmitter of this para- 
site is evidently Culex quinquefasciatus, the common house-mosquito of the 
tropics. This is the species which has been used by Bancroft in Australia under 
the name Culez ciliaris, by Manson in China and by Low in Santa Lucia under 
the name Culex fatigans, and by Lebredo at Havana as Culex pipiens. There is 
every reason for believing that these observers all had this same mosquito, which 
is so widely distributed and abundant throughout the tropical and subtropical 
regions. James, in India, found Anopheles rossi, and a second undetermined 
species of the same genus, to be efficient hosts; the same was found to be true 
with Anopheles costalis by Annett, Dutton and Elliott in West Africa. For 
Italy and Spain Anopheles maculipennis, A. bifurcatus, A. pseudopictus and 
Culex penicillaris are reported as transmitters. The identification of this last 
mosquito seems open to doubt. Other species of mosquitoes in which Filaria has 
been found to develop are Anopheles annulipes, A. albimanus, A. minutus, A. 
nigerrimus, Aédes calopus, Mansonioides uniformis and Mansonia pseudo- 
titillans (?=titillans). James, in his experiments, found that Filaria bancrofti 
developed partially in Culex microannulatus and Aédes scutellaris. 
