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Parasitic Worms 
according to the temperature at which they develop best, some only 
developing at a temperature lower than that of the host, some being 
relatively indifferent and others doing best at the temperature of the 
host. In this way they read an evidence of the manner in which 
parasitic Nematodes have become adapted to their modes of life. 
Hamill (190G) has confirmed the earlier view of Weinland that there is 
in Ascaris an antibody which resists tryptic digestion. This question 
of the nature of the substances secreted by parasitic worms is a very 
wide one and has called forth a considerable amount of work. The idea 
of toxins has bulked largely in medical literature dealing with the 
subject, but, although there is a prima facie element of reason in the idea, 
no satisfactory experimental or clinical demonstration of a general nature 
has }et been forthcoming. The most important of recent work on this 
matter is that of Flury (1912) and Weinberg (1912). Another matter 
which may be most appropriately referred to here is that of the formation 
of pearls by parasitic worms in their larval stage. This was first 
brought into prominence about ten years ago by Jameson who showed 
that pearls in the common edible mussel owed their origin to the 
presence of larval Trematodes. A few years later Herdman and Hornell 
advanced the view that Ceylon pearls had a similar origin, the agent in 
this case being a larval tape-worm ( Tetrarhynchus ). This view has led 
to an economic attempt to encourage the presence of this tape-worm on 
oyster beds so as to increase the yield of pearls. Doubts, however, have 
been cast on the correctness of these observations by Jameson (1912) 
who considers that some other causal agent must be sought for in the 
case of the Ceylon pearl oyster. 
Coming now to a consideration of the economic, and more particularly 
the medical relations of parasitic worms, we find that many problems 
involving the health of both men and animals have been extensively 
investigated and that a fair measure of improvement has resulted. The 
disease which has attracted most attention during these latter years is 
Schistosomiasis or Bilharziosis. This is the particularly intractable 
disease due to the presence of blood-flukes ( Schistosomum) and although 
not so notorious or widespread as Ankylostomiasis or Filariasis it is 
usually more difficult to treat and indeed no cure has yet been 
discovered. The chief work done in regard to the Egyptian form of the 
disease has been of a clinical and pathological nature by Goebel (1907), 
Glaesel (1910) and Letulle (1911). These contributions, although they 
have served to fix a definite pathological picture of the disease, have not 
added materially to our knowledge of the subject. A more important 
