163 DEPARTMENT OF THE NATAL SERVICE 



8 GEORGE V, A. 1918 



with Saprolegnia remained healthy. Dace, sea trout and one gold fish inocu- 

 lated with Saprolegnia and B. salmonis pestis died in various periods of time 

 (2 to 18 days) except the gold fish which died after inoculation and showed signs 

 of the fungus on the gill covers. No attempt was made to make cultures from 

 the dead gold fish." 



Patterson concludes that:— 



" Saprolegnia grows on live fish in the presence of the organism, which 

 breaks down the siiperficial tissues and forms a suitable nidus for the fungus to 

 grow on." 



I had no Saprolegnia to try similar experiments. 



The difficulty of obtaining and keeping fish for experiments in a laboratory 

 unequipped for such work, and the difiiculty because of lack of laboratory equipment 

 to carry out experimental work at the hatchery, will have to be overcome before any 

 decisive experiments can be undertaken. 



It is, however, significant that all organs apparently healthy in the salmon 

 examined contained bacteria in large numbers, and of comparatively few species, and 

 I am unable to state or find in any literature or obtain information as to the bacterial 

 content of the normal organs of fish, or how soon after death, and to what extent, these 

 organs are invaded by bacteria. Very large numbers of bacteria were found in the 

 eggs from a number of the fungus-infected salmon, and under normal conditions one 

 would scarcely expect to find so many bacteria present. 



All that can be stated at present is that Patterson's organism, B. salmonis pestis, 

 was not found, and that the large number of bacteria present accompanying the 

 Saprolegnia may have some pathogenic role, but the rules of proof (Koch's postulates) 

 would have to be worked out where fish, the means of keeping them, and laboratory 

 ■facilities are provided. 



