about the causes and the method of dealing with natural 

 occurrences, the mechanism of which is infinitely more com- 

 plicated than that of the culinary apparatus while their 

 ignorance of even the elements of the problem is absolute. 



Surely it does not want any science, but only a little 

 common sense, to see that the first step in a case of this 

 kind is to find out the exact nature and causes of the phe- 

 nomena over which we wish to exert a control. The foun- 

 dations of such knowledge in respect of the salmon disease 

 were laid by the late Mr. Stirling, in a series of papers 

 which appeared in 1878 and 1879, and I have been trying 

 for the last two years to raise the superstructure, which, 

 however, is, as yet, by no means complete. 



If the fluffy whitish coat which is so characteristic of the 

 diseased skin and is sometimes tenacious enough to be 

 stripped off in flakes like wet paper is examined micro- 

 scopically, it is seen to consist chiefly of a tangled mass of 

 fine filaments, on an average about 2^oo tn f an mcn m 

 diameter, which are at once recognisable as the stems (or 

 hyphtz as they are technically termed) of a fungus (Sapro- 

 legniaferax), similar to those which are known as " moulds," 

 and which commonly grow upon, and obtain their nourish- 

 ment from, decaying organic bodies. The so-called " blue 

 mould " (Penicillium glaucum), which attacks all sorts of 

 dead organic bodies from cheese and jam to old shoes, is a 

 familiar example of these plants, which, however trouble- 

 some to housewives, play a very important part in the 

 economy of nature as scavengers, by whose agency dead and 

 decomposing organic bodies are cleared away. All the fungi 

 which thus prey on dead animals and vegetables are known 

 as Saprophytes, a term which may be pretty nearly para- 

 phrased by " rot-plants." 



