125 



NOTES, COMMUNICATIONS, AND REVIEWS. 



On Unicellular Animal Parasites.^ — A Review. — One of 

 the most important discoveries of recent times, is that 

 minute animal parasites of unicellular structure are the 

 agents responsible for many of the most ravaging diseases of 

 man and the lower animals. Such organisms are members of 

 that division of the animal kingdom known as the Protozoa. 

 Comparatively few subjects have leaped into prominence with 

 the rapidity that has been the fortune of the study of patliogenic 

 Protozoa. It was not until Laveran's discovery of the malaria 

 parasite in 1880 that the presence of these unseen foes was ever 

 seriously entertained. Yet we know to-day that diseases of 

 man, and also of horses, cattle, dogs, poultry, game, fish, bees, 

 and silkworms are due to their ravages. Probably every species 

 of verte])rate animal, and a large number of invertebrates, 

 support one or more species of Protozoa within their bodies. 

 Numerous forms are known to live in the blood of vertebrates, 

 others penetrate the digestive system, some live within th^ 

 muscles, in the reproductive system and in otber parts — in fact 

 few organs can be declared immune from their presence. The 

 methods by which these parasites gain entrance into the tissues 

 of their hosts can only be ascertained after difficult and 

 prolonged research, and in numerous instances the mode of trans- 

 mission still remains to be discovered. Many of the parasites 

 are disseminated from one animal to another by their spores 

 contaminating the food or drink, a method which is known as 

 contaminative infection. Others are introduced through the 

 punctures made by insects provided with piercing mouth parts, 

 or by means of the bites of ticks — a type of infection which is 

 termed the inoculation method. In the cases of fishes and 

 amphibia, the protozoan parasites are conveyed from one host 

 to another by means of the bites of leeches, which are abundant 

 denizens of the waters in which they live. It must be 

 remembered, however, that the greater number of the Protozoa 

 are non-pathogenic, free-living organisms and abound in water, 

 in the soil and elsewhere. Others live harmlessly in the 

 digestive canal of various animals without causing any observ- 

 able ill effects, but it is with the pathogenic rather than the 

 harmless forms that Drs. Fantham and Porter are primarily 

 concerned. The book before us has been written, they tell us, 

 to satisfy a demand for a scientific but readable account of 

 those forms of Protozoa which produce disease. It is essentially 



' H. B. Fantham and Annie Porter. — Some Mimite Animal Paranites, or 

 UrDseen Foes In The Animal World. London, Methuen & Co., Ltd. 1914. 

 Pp. xi. k. HI 9. With frontispiece and fifty-six text figures, 5/- net. 



