W. Nicoll 
385 
Martin has published an interesting paper on the conditions of embryonic 
development of parasitic Nematodes in general, while Kautzsch has dealt at 
length with certain anomalies in the development of Ascaris. With regard to 
“free living” Nematodes the most economically important work appears to 
be that of Stift on the life-history of root Nematodes. 
turning now to what is, from a medical point of view, the subject of 
greatest interest, namely the relation of parasitic worms to disease we find 
that quite an extensive literature has accumulated, much of it being of the 
very highest order. First in point of importance and by reason of the large 
amount of excellent research work done in regard to it is Bilharziasis. While 
not having quite such a widespread distribution as the hookworms or the 
filarial worms the Bilharzia species are the cause of some of the most serious 
pathological conditions originated by any worm parasite, and the gravity of 
such conditions is accentuated by the fact of their comparative intractability 
to medical treatment. 
Although the disease has been known apparently from very ancient times 
it is only within the past seventy years that its causal agent has been definitely 
recognized. The worm is thus a slightly more modern acquaintance than its 
rival Ancylostoma duodenale though both, so far as may be judged from historical 
evidence, were familiar to the people of ancient Egypt some thousands of 
years ago (Khalil). 
Much as one may feel tempted to enter on a detailed discussion of the 
administrative measures, necessary or advisable for the control of this disease, 
it seems to me that the conclusions reached by Leiper sum up the position 
sufficiently clearly. These have been quoted by more than one reviewer but 
their administrative importance justifies further repetition. They are that 
(1) transient collections of water are quite safe after recent contamination; 
(2) all permanent collections of water such as the river Nile, canals, marshes 
and birkets are potentially dangerous, depending upon the presence of the 
essential intermediate host; (3) the removal of infected persons from a specified 
area would have no effect, at least for some months, in reducing the liability 
to infection (i.e. of other persons), as the intermediate hosts continue to dis¬ 
charge infective larval forms for a prolonged period; (4) infected persons 
cannot reinfect themselves or spread the disease directly to others. They could 
only convey the disease to those parts of the world where suitable local mol¬ 
luscs were present to act as intermediate hosts; (5) infection actually takes 
place both by the mouth and through the skin; (6) infection in towns is 
acquired from unjiltered water which, in addition to filtered water, is still 
supplied even in Cairo though it is delivered by a separate system of pipes; 
(7) eradication can be effected without the cooperation of infected individuals 
by destroying the molluscan intermediate hosts. 
In these respects Leiper’s conclusions differ radically from those of Looss, 
the pivotal point being, of course, the infective stage of the worm ( cercaria 
instead of miracidium) . They are, undoubtedly, of the very highest importance 
