286 DE. T. S. COBBOLD ON THE LAEG^j; HUMAN FLUKE. 



minithologist, who at tlie time was still in possession of his eye- 

 sight. Here, again, however, no second instance of the occurrence 

 of the "parasite" was made known until thirty-five years had 

 elapsed. In the year 1869 Professor Verrill described what he 

 very naturally supposed to be a new entozoon infesting the hogs 

 of the United States. He called the species Sderostoma pingui- 

 cola. Specimens of these worms, however, having been forwarded 

 to me by Professor Pletcher, of Indianapolis, I at once saw that 

 Verrill's Sclerostomafa were the Steplianuri of Diesing and bat- 

 terer. Subsequently also I detected this self-same entozoon in 

 a batch of parasites sent from Australia to the Microscopical So- 

 ciety of London for the purpose of identification. It thus ap- 

 pears, from the case of Steplianurus, that a parasite capable of 

 producing serious miscliief and even death amongst well-known 

 animals may evade rediscovery for a very long period of time, and 

 this, too, notwithstanding the ever-increasing number of natural- 

 history observers. Of more importance, also, is the consideration 

 that many a species, Mtherto assumed to be extremely rare and 

 local, may turn out to be both numerically abundant and of wide 

 geographical distribution. As will be seen in the sequel, the latter 

 part of this inference applies with some force to the parasite now 

 before us ; and I should not be at all surprised if its supposed 

 rarity were eventually proven to be without foundation in fact. 



For an opportunity of securing fresh examples of the Distoma 

 crassum I stand indebted to Dr. Greorge Johnson, P.E.S., who in 

 the spring of last year recommended two of his patients — a mis- 

 sionary and his wife — to call oii me in order that I might have 

 an opportunity of examining and identifying the parasites that 

 were occasionally escaping their bearers |;er vias naturalcs. I 

 should mention that Dr. Johnson readily recognized the trema- 

 tode character of the helminths, and that he advised accordingly. 

 Eeserving purely professional details for publication elsewhere, I 

 have to state that from the missionary and his partner I learned 

 that they had been resident in China for about four years. During 

 that time they had together freely partaken of fresh vegetables in 

 the form of salad, and also occasionally of oysters, but more par- 

 ticularly of fish, which, in common with the oysters, abound in the 

 neighbourhood of Ningpo. Prom their statements it appeared to 

 me that to one or other of these sources we must look for an ex- 

 planation of the fact of their concurrent infection. Fluke larvae, 

 as we know, abound in mollusks and fish ; but whether any of the 



