SEA-FISHERIES LABORATORY. 187 



ducing cells are stimulated to growth in abnormal 

 positions ? 



Environment, including all external conditions, has 

 been ruled out by some writers on this subject because of 

 the width of distribution of cancer in the animal 

 kingdom, and, therefore, the very varied conditions under 

 which it may occur. But surely to do so is to take an 

 unfortunate view of the conditions of the problem. 

 Given the predisposing cause universally present in 

 organisms, those comparatively few cases in which the 

 abnormal processes take place may be regarded as offering 

 us the opportunity of determining what the exciting 

 cause may be which stimulates to, or permits, further 

 action. Cancer research is now a biological and bio- 

 chemical investigation, and any observations upon the 

 environment of abnormal growths in lower animals, or 

 upon the conditions surrounding diseased cells and tissues, 

 may at any time throw light upon the matter. 



In last year's Report I had an article on "Sewage and 

 Shellfish," in which I gave and discussed reports from 

 Mr. Dawson on the pollution of mussel beds, and from 

 Mr. Johnstone on their bacteriology. Mr. Johnstone 

 has continued that work during the past year in the form 

 of a bacteriological investigation of the shell-fish beds 

 of the district in relation to pollution by sewage. In his 

 article given below, he deals with the mussel beds of the 

 Mersey and those of the Lune estuary, and for com- 

 parison he also gives the results of the examination of 

 deep-sea oysters from pure water. With, his general 

 conclusions I entirely agree, although one cannot help 

 regretting that it seems impossible to define any standard 

 of practical purity which might be recognised and per- 

 mitted in shell-fish sold as human food. 



Since the bacteriological outfit has been established 



