136 



ON A COENURUS IN THE RAT. 



By M. turner, B.Sc. 



{Helminthological Department, London School of Tropical Medicine.) 



(With 1 Text-figure.) 



The Rat plays so important a part in economic life and welfare of all 

 peoples that, for many years, it has been the subject of minute and routine 

 examinations. Because of this, its parasites are well-known and have been 

 described in several important monographs. In 1908, Dr A. E. Shipley, 

 Master of Christ's College, Cambridge took "Rats and their Animal 

 Parasites" as the subject of his Presidential Address to the Association 

 of Economic Biologists, and the same theme formed a considerable part 

 of the Presidential Address of Dr Burton Cleland to the Royal Society 

 of New South Wales in 1918. 



One of the most common parasites of the rat is the larval tapeworm, 

 Cysticercus fasciolaris, which infests the liver. Owing to the atypical 

 appearance of this larval tapeworm it is frequently received by the 

 Helminthological Department of the London School of Tropical Medicine 

 for special diagnosis. With a similar object Dr W. M. Graham some years 

 ago forwarded a collection of parasitic worms, made during a routine 

 examination of rats at Accra, in connection with an outbreak of plague 

 on the Gold Coast. The collection included several specimens of Cysti- 

 cercus fasciolaris, and also a large ellipsoidal cyst which had been found 

 in the abdomen of a rat. More recently Dr J. A. Murray, Director of the 

 Imperial Cancer Research Laboratories, kindly sent two tapeworm cysts 

 which came under his notice while examining mice purchased in London. 

 Through the courtesy of Professor Leiper I was able to investigate all 

 three cysts in detail. 



The usual form of a larval tapeworm is the Cysticercus, which is a blad- 

 der-like cyst that bears on its internal surface one bud. In the definitive 

 host this bud develops into the head of the adult worm. The cysts found 

 in the rat and niire agree with the Cysticercus in having a vesicular 

 shape but dift'ei' Iroiii it in having numerous buds instead of only one. 

 For this reason the three cysts from the rat and mice belong to the group 

 of polycephalous larval tapeworms known as "Coenurus." 



