388 Parasitic Worms 
far-reaching which has been accomplished on the subject since that of Looss 
in Egypt. 
One of the most interesting biological facts revealed by the work of 
the Commission is that hookworm larvae commonly live in an unensheathed 
state in the soil. Hitherto it has generally been believed that the unsheathing 
takes place at the moment the larvae penetrate the skin of their host, though 
the occurrence of unsheathed mature larvae in experimental cultures must 
be a matter of fairly common observation. The report also deals with several 
matters of administrative importance. 
Another species of hookworm, Ancylostoma ceylanicum, is dealt with by 
several authors and its geographical distribution forms the subject of a paper 
by I hie (1918). 
The matter of next greatest economic importance appears to be Oncho¬ 
cerciasis (worm nodule disease in cattle). This is a subject our knowledge of 
which is of comparatively recent date. Although the disease has been recog¬ 
nized for many years scientific interest in it dates only from the past twenty 
years. Curiously enough it is in Australia, the land of imported cattle, that 
the condition has given rise to most discussion and in consequence the bulk of 
the work has been done by investigators in Australia. The most considerable 
contribution to the subject is that of Sweet (1915) who in the course of a tour 
round the world visited most of the countries in which the disease is known 
or suspected to occur. Her paper forms therefore a very useful summary of 
the geographical distribution of the parasite and contains many interesting 
observations on local conditions as they may affect the spread of the infection. 
Previously (1912) Harvey Johnston published a summary of existing know¬ 
ledge on the subject at that time. The most important experimental work, 
however, is that of Burton Cleland (1914) who attacked the problem in an 
energetic manner but without solving the mystery of transmission. I have 
personally (1914) carried out some experiments on the nodules both in vivo 
and in vitro without any striking result except to demonstrate that the larvae 
can and do penetrate the thick capsule of the nodule in which they are enclosed 
and thus get into a situation in which a potential intermediate host may 
reach them. No intermediate host has, however, been discovered so far and 
practically no definite clue is available to point the way to a possible life- 
history. The fact that similar worms cause disease in man ( Onchocerca volvulus) 
and in horses (0. caecutiens ) gives the subject an economic interest which is 
not confined to cattle. Rodhain and van den Branden (1916) and Robles (1919) 
have made interesting contributions to our knowledge of the human form of 
Onchocerciasis which has received further treatment at the hands of Brumpt 
(1920), Desoil (1920), Montpellier and Lacroix (1920), and most recently 
Ouzilleau, Laigret and Lefron (1921). Further remarks on cervical Oncho¬ 
cerciasis of horses have been published by Railliet (1919). 
Of much greater medical interest and importance is hydatid disease 
(Echinococcosis). This is another disease which has afflicted Australia in 
