OF NEW SOUTH WALES. 417 



larly among the Entozoa, by the researches of Professor Van 

 Beneden, Dr. Cobbokl, and others, and their results have shown 

 clearly the advantages to be derived, in a sanitary point of view, 

 from our. improved knowledge. As regards the mere cure of 

 disease, I do not know that we have gained much. Medical men 

 knew how to destroy a Tcenia, and eradicate the Itch, long before 

 they know the history of the one, or that the other was caused by 

 a subcutaneous Acarus. But the value of these discoveries as a 

 means to the prevention of disease is incalculable. Thus, since it 

 has been ascertained that the Gysticercus cellulosce, or measle 

 of the pig, is the larval or scolex condition of the Tcenia solium of 

 the man, we know that no one can suffer from that tapeworm unless 

 he is an eater of raw or under-cooked pork. In the same way the 

 Gysticercus of the calf becomes a perfect Tcenia mecliocanellata in 

 the human being, but it can only be introduced there by eating 

 uncooked veal or beef. 



The discovery, due chiefly to Van Beneden and Dr. Cobbold, 

 that the Entozoa, to complete their cycle of existence, must in- 

 habit under widely different forms, two equally widely different 

 hosts, furnishes us with the means of understanding much which 

 was previously unintelligible, and gives us, at the same time, a 

 possible explanation of subjects on which we are, up to the present 

 time, quite in the dark. 



For instance, thei*e are some most formidable diseases which are 

 universally ascribed to the action of poisonous germs inhaled from 

 sewers or cesspools, or swallowed in impure water — such as Diph- 

 theria, Dysentery, Typhoid or Enteric Fever, and Cholera. The 

 first of these we know to be caused by a species of Oiclium, a fungus 

 of the same genus as that which produces the vine disease, Oidium 

 Tuckeri, but we know nothing of the history of the plant beyond 

 that it seems to thrive best in ill-drained localities, and that the 

 disease it causes is not directly infectious. Dysentery also is not 

 directly infectious, though when it breaks out in any locality it 

 generally spreads with amazing rapidity. Typhoid Fever and 



