ESSAY-REVIEWS 149 



There is a lengthy account of the genus Schistosoma and of its distribution and 

 pathogenic action on man. An inserted slip records the characteristics of adult 

 S. hcemotobium and S. mansoni as set forth by the recent Bilharzia Commission in 

 Egypt. There is also a good resume of the life-history of S . japonicum, the first of 

 these organisms to be well investigated, Japanese scientists again being the 

 pioneers. 



The Cestoda are treated on the same plan as the Trematoda. The intro- 

 ductory portion contains anatomical details and an account of the general lines of 

 development of the group. Some of the new diagrams illustrating developmental 

 stages {e.g., cysticercus, cysticercoids) are crude in execution, and contrast there- 

 fore with the majority. Among the more interesting genera described is Di- 

 bothriocephalus, the "broad tapeworm" of man, French Switzerland and the 

 Baltic Provinces of Russia being the distribution centres for Europe. It is fre- 

 quent in Germany, particularly in East Prussia. Man acquires the parasite by 

 ingesting the developmental plerocercoid stage with raw or imperfectly cooked 

 fish. Sparganum proliferum is of interest as it forms capsules beneath the skin. 

 An account is given of Dipylidium and Hymenolepis, parasitic in dogs, cats, and 

 rodents, the transmission being effected by the agency of fleas in some cases. 

 The various species of Taenia are described, and statistics given as to the fre- 

 quency of Taenia infection in man and pigs in Germany. 



The Nematodes are a huge group of parasites, many of which occur only occa- 

 sionally in man. Others unfortunately are well known. The life-cycle of most of 

 these parasites is described and illustrated. The guinea-worm has long been 

 known. The efforts of the Americans to eradicate Ancylostoma and Necator, 

 responsible for so much feebleness among certain sections of the public, have 

 made them known. The life-histories of the various worms, and the resemblances 

 between certain of their immature stages and those of other, relatively harmless, 

 young or adult worms, are set forth. Similarly information respecting filariasis 

 and trichinous conditions, infections with whipworms and strongyles, with Ascaris 

 and other threadworms can be found. The section closes with some notes on 

 the preservation of worms and their eggs. 



Section III., Arthropod A, by Prof. Theobald, deals with the two parasitic 

 groups of these organisms, the Arachnoidea and the Insecta. There is a useful 

 series of diagnostic tables given in this section. 



Two orders of Arachnoidea are considered, the Acarina and the Linguatulidae. 

 Certain genera of the Acarina receive a good deal of attention. Many are 

 parasites of man when he is available as host, though they may spend the greater 

 part of their lives on domestic or wild animals, or on plants. Trombidium in its 

 larval forms is common in barley fields, producing autumn erythema in men whom 

 they attack. Small mammals, such as hares and moles, are the normal hosts, but 

 horses and cattle may be attacked. Pediculoides infest cereals and the insect 

 pests found in cereals. They may attack men handling corn. Other mites lead 

 endoparasitic existences in the tissues and air sacs of birds, a few having been 

 suspected of living endoparasitically in man. Certain Gamasidae may attack 

 man. Thus, the "red fowl mite," Dermanyssus, can attack men who have to 

 enter dirty poultry houses, or attend to infected pigeon lofts. These parasites 

 are described more particularly with respect to their habits, rather than to their 

 structure. 



The Ixodidas are more important to man economically, since certain of them 

 are concerned in the propagation of relapsing fever in man and red water, 

 malignant jaundice, and heart water in cattle, sheep, and dogs. A generalised 



