120 SECTIONAL ADDRESSES. 
feeces the encysted stage which is capable of infecting other persons. 
Whether an infected person will suffer from dysentery or act as a 
healthy ‘ carrier ’ apparently depends upon his own susceptibility rather 
than on any difference in the virulence of different strains of the 
Entamceba. 
In all work with human Entamcebe there is need for critical deter- 
mination of the species, for, in addition to H. histolytica, a closely 
similar species, E. coli, is a common inhabitant of the intestine. This, 
however, is a harmless commensal, feeding on bacteria and fragments 
derived from the host’s food. The distinction between the two species 
rests chiefly upon the characters of the nuclei and of the mature cyst— 
quadrinucleate in histolytica and octonucleate in coli—and considerable 
care and technical skill are requisite in many cases before a diagnosis 
can be given. And yet this distinction is definitely necessary in prac- 
tice, for indiscriminate treatment of persons with Entamceba is indefen- 
sible ; treatment is only for those with histolytica; it is useless for those 
with coli, and subjects them needlessly to an unpleasant experience. 
A notable result of recent work is the proof that the more common 
intestinal Protozoa, formerly believed to be restricted to warmer coun- 
tries, occur indigenously in Britain. ‘his was first established by a 
group of observers in this city, and has been confirmed and extended by 
subsequent workers. There is good reason for believing that in this 
country the incidence of infection with EH. histolytica is about 7 to 
10 per cent., and with H. coli about five times as great (Dobell). 
The discovery (1903) of Leishmania, the organism of kala azar and 
of oriental sore, added another to the list of important human patho- 
genic Protozoa, but the mode of transmission of this flagellate has not 
yet been proved. é 
Of the problems presented by the parasitic worms the most momen- 
tous are those associated with Ancylostoma and its near relative 
Necator, which are prevalent in countries lying between 369N. and 
30° S.—a zone which contains more than half the population of the 
earth. Heavy infection with Ancylostoma or with Necator produces 
severe anemia, and reduces the host’s physical and mental efficiency 
to a serious degree. Until 1898 there was no suggestion that infection 
was acquired in any other way than by the mouth, but in that year Looss 
published his first communication on the entry of the larve of Ancy- 
lostoma through the skin, and in 1903 gave‘an account of further experi- 
ments which proved that dermal infection ‘resulted in the presence 
of worms in the intestine. At the meeting of this Association in Cam- 
bridge in 1904 Looss demonstrated to a small company his microscopical 
preparations showing the path of migration of the larve. His investiga- 
tions served to establish the importance of the skin as the chief portal 
of entry of Ancylostoma, and pointed the way to effective methods of 
prevention against infection. 
__ Another notable advance in helminthology is the working out of the 
life-cycle of Schistosoma (Bilharzia)—a genus of trematode worms 
causing much suffering in Egypt and elsewhere in Africa, as well as 
