o4 ENTOZOA OF RATS AMJ MICE. 



Between Seiitejnber 191J9 and February 191(>. an almost 

 daily examination of rats and mice for the presence of entozoa 

 was made and careful records kept, Mr. W. Thompson 

 greatly assisting me in this work. Besides, there were 

 plentj' of other casual searches made prior to, and after, 

 the period mentioned. During the stated time 28 ont of 119 

 specimens of the house rat, Epimys raftus, Avere found to 

 contain some intestinal or stomach helminths (23.5%) ; 

 21 out of 100 red rats, Ep. alexandrinus (21%) ; 51 out of 

 121 brown rats, E2j. norvegicus (42.1%) : and 34 out of 73 

 mice, Mils musculus (46.6%). 



Tcenia fceniceformis Bl. 



The cystic stage of this parasite, generally known in 

 its larv"al forms as Cysticercus fasciolaris R. and in its 

 adult stage as Tcenia crassicollis, occurs in Australian rats 

 and mice. It was found rarely in Ejnmys alexandrinus 

 in Sydney, (only 3% infected), but more commonly in E. 

 norvegicus and Mus musculus, though even in these the 

 percentage infection was not high. Leidy (1879) examined 

 500 brown rats (E. norvegicus) in Philadelphia and found 

 •only six to be free from this cj-st. 



The greatest number that I have found in one animal 

 was 189, most of them small, from a brown rat (February, 

 1909), very little liver substance being visible. In the liver 

 of a mouse, no less than six full-grown cysts and a small 

 one Avere detected (Feb. 1909), some of them being pendulous 

 and some of them more or less imbedded, very little liver 

 tissue being seen. 



The largest measured l)y me was found on opening 

 the membrane of the cyst to be nine and a-half inches long 

 with a tim- bladder. It was removed (Feb. 1909) from a 

 pendulous cyst from Ejj. norvegicus. 



McCoy (19106. pp. 65, 66) in writing on the tumours 

 of lats, mentioned the frequency of sarcoma in the liver, 

 the majority of such sarcomata being associated with this 

 Cysticercus. Blanehard (1909, p. 158) also referred to the 

 association, mentioning that Regaud had found the larva 

 in the middle of a peritoneal sarcoma of a rat, and disagree- 

 ing with Borrels opinion that the Cysticercus A\as the cause. 

 He believed that the })arasite had penetrated a preformed 



