COPEPODA 



739 



CLASS IV. CRUSTACEA Lamarck, 1815. 



Aquatic Arthropoda which breathe by means of gills. 



Crustaceans can hardly be considered as human parasites, for they have 

 very rarely occurred as such — e.g., Caligus curtus in the cornea, and Gammarus 

 pulex in the stomach.' 



ORDER COPEPODA Latreille, 1831. 



It must, however, be remembered that the Copepoda are of importance, 

 because a species of Cyclops has been found to be the intermediary host of 

 Dracunculus medinensis, the guinea-worm. An excellent paper on the species 

 found on the Gold Coast is contributed by Graham to vol. i. of the ' Annals of 

 Tropical Medicine and Parasitology.' The Cyclops live in fresh water in any 

 ditch, pond, or well. 



Prophylaxis. — It is recommended to treat a well with sufhcient quick- 

 lime to render the water suddenly hot in order to kill these crustaceans. The 

 well must, of course, be closed for some time after this proceeding, until the 

 percentage of lime has diminished to reasonable proportions. A simpler 

 remedy is to boil all water before drinking. It has been also suggested to add 

 I pound of caustic soda to 180 gallons of water = 0*07 per cent, for the same 

 purpose. Leiper's recommendation is, however, the best, and this is to raise 



Fig. 361. — Cyclops bp. (?). 



the temperature of the well-water to 65° C. by blowing in steam, as he finds 

 that all Cyclops die if the water is raised to 35° C. He calculates that it 

 requires 87 gallons of water as steam to raise 1,000 gallons of water from 15° 

 to 65° C, and that this requires i pound of coal or its equivalent in oil per 

 gallon of water, and that for every square foot of grate 1 5 pounds of coal can 

 be burnt per hour, so that if the grate is i square foot it will require 11 = 6 

 hours to raise 87 gallons of water as steam — i.e., 12 square feet of grate give 

 90 gallons of water as steam in half an hour. 



CLASS V. CHILOPODA Latreille, 1837, 



Arthropoda with three protthomeres. The first post-oral somite is the 

 mandibular ; the second and third post-oral somites carry the maxillae, while 

 the fourth has its appendages converted into very large powerful jaws, which 

 are provided with poison glands. The remaining somites carry single-clawed 



