of the Fishery Board for Scotland. 45 



as not to cause any physical clogging of the gills of the fish, and as to 

 ensure an adequate supply of dissolved oxygen for purposes of respiratiou, 

 such sewage may have no harmful effect on the fish inhabiting any such 

 areas. 



To sum up, it may be said that, although on the one hand the evidence 

 appears to indicate that fish do not suffer readily from the ingestion of 

 bacteria, nor from the presence of sewage in the medium in which they are 

 living, so long as its dilution is sufficient to prevent clogging of the gills, and 

 sufficient to provide an adequate supply of dissolved oxygen for purposes of 

 respiration, yet it further appears from the evidence of this investigation that 

 such occurrences as outbreaks of disease amongst fish due xo the presence of 

 sewage-borne micro-organisms is a possibility of some significance to Health 

 Authorities in whose sanitary areas sewage is being deposited in rivers, 

 estuaries, or on to the sea-shore. As a corollary the nbove conclusions 

 further serve to emphasise the importance of the possibility of the trans- 

 mission of disease by fish inhabiting sewage-polluted areas, and more 

 especially by shell-fish, whose peculiar constitution, mode of life, feeding, 

 and texture render them specially liable to harbour pathogenic bacteria. 



In conclusion, I wish to avail myself of this opportunity of expressing my 

 indebtedness to Dr. T. W. Fulton, Scientific Superintendent, for the facilities 

 and assistance which I have readily received while working in the Marine 

 Laboratory. 



