KEVIEW — TROPICAL MEDICINE, ETC. 145 



of the intestine and liver, such as insects play in the etiology of blood infections. He advances evidence to Parasites — 



support the view from the records of both human and comparative parasitology. While recognising fully that the caiUiiiiieti 



infections are bacterial, he emphasises the necessity of some inoculating agent as, in a sense, the most important 



element, since pathogenic bacteria are generally present in the alimentary canal. No one can doubt, he maintains, 



that Eberth's bacillus is the agent of typhoid fever, but there is reason for regarding it as innocuous if the 



intestine is undamaged. In a population diinking contaminated water only a few persons in reality are infected. 



Any intestinal parasite capable of inflicting a wound may infect the host if the bacillus be present. The infecting 



■agent may be an Ascarid, a hook worm, a fly larva ; most commonly Quiart believes it to be the whip worm 



(Trichuris), which bores into the folds of the intestinal mucosa with its attenuated anterior end. This parasite 



Quiart (1901) calls the lancet of inoculation, and demonstrated its presence in eleven out of twelve typhoid 



cases in one group. 



(&) Morphological. — It is difficult to find any definite explanation of the causes of the 

 morphological changes which result from the influence of the parasite on its host. Ward 

 suggests that the stimulation of growth by parasites may be due to a chemical stimulus, and 

 that the stimulating substance is a poison, a proposition which brings us to 



(f) Physiological. — 1. The question of the absorption of nutriment takes first place in 

 this connection. The parasite requires a certain amount of food matter to carry on its vital 

 processes, and this is furnished, partially or fully digested, by the host animal. Some 

 interesting details follow, but they cannot be given here. 



2. Important efi'ects are produced by increase in size of the parasite. Example : 

 Interference with function produced by a large hydatid cyst of the liver, 



3. Eeflex nervous action. This, however, is pure hypothesis. 



4. Eetardation of development of host organism. Example : Parasitic castration 

 (Giard). 



5. Destruction of tissue of host. Example : The feeding of the liver fluke on liver 

 tissue and the resulting growth of connective tissue. Much depends on the number of 

 parasites concerned. 



6. Inhibition of the coagulative power of the blood. Example : Agchylostomiasis. 

 (Loeb and Smith). 



7. Production of toxic material by the parasite. This may be waste, excretory matter, 

 or it may be an actual toxic substance. Thus if an hydatid cyst rupture, serious results may 

 ensue from the absorption of the toxic material liberated. A strong argument in favour of 

 this toxic theory is the production of eosinophilia. 



Production of anaemia as by Dibothriocephalns latus. The whole of this paper is well 

 worthy of careful study and can be obtained in the form of a reprint. 



A very similar article is that by Shipley and Fearnsides.' They take up the different 

 groups of the metazoan parasites, and consider the effects produced by difl'erent species 

 under each group. There is much of interest and numerous references, while special 

 attention is devoted to the question of eosinophilia. 



Weinberg- communicates an important paper on the parts played by helminths and 

 their larvae in the transport of pathogenic microbes. He believes that most helminths 

 favour the incubation of the intestinal mucosa by microbes, and states that : — • 



The method of inoculation diilers in different species of parasites. Thus certain nematodes, such as 

 Tnchocephalus, Oxyiiris, Sclerostoma, Physahyptcra, Spiroptera, which are capable of fixing themselves on the 

 intestinal wall, inoculate directly with the microbes lying on the surface of their bodies. Others such as the 

 Ascarides, though incapable of fixing themselves, favour infection by superficial gnawing of the mucous membrane 

 and by causing small foci of congestion, which may develop into secondary centres of inflammation, and even of 

 ulceration. Cestodes can also cause lesions of the mucosa. Although incapable of piercing it, their suckers give 

 rise to foci of congestion, which may be inoculated with the microbes always to be found on these organs. 

 A considerable infiltration of phagocytes follows, but under certain circumstances their action may not suifice 

 to prevent inflammatory processes, and even ulceration. 



Not only are helminths usually covered with microbes externally, but their intestinal contents may include 

 a most extensive microbic flora, and they therefore constitute a serious danger to their hosts when they remain 

 fixed for any length of time to the mucous membrane. Larval forms of these parasites penetrate the intestinal 

 wall in large numbers, carrying microbes with them, and so set up submucous suppurations, aortitis and 

 sub-peritoneal inflammatory nodules. 



1 Shipley, A. E., and Feamsides, E. Q. (March 30th, 1906), "The Effects of Metazoan Parasites on their 

 Hosts." Journal of Economic Bioloyy, Vol. I. No. 2. 



' Weinberg, M. (.June 25th, 1907), " Du role dea Helminthes, des larves d'Helminthes et des larves d'Insectes 

 dans la transmission du Microbes pathogeues." Ann. Ue I'Insl. Past., t. XXI. 



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