JOHN F. NORTON 375 



municipal supplies in Europe utilizing this method, it has found little favor in this 

 country. There are certain important difficulties. Water, to be treated satisfactorily, 

 must be relatively pure from a bacterial standpoint and free from suspended matter 

 or color. Prefiltration is therefore almost a necessity. To get the best results a battery 

 of lamps must be used with a consequent high operating cost. It is doubtful whether 

 ultra-violet sterilization will ever become an important means for purification of 

 municipal water supplies in this country. 



In the past fifteen years there has been an increasing use of ultra-violet sterilizers 

 for swimming-pool purification. The sterilizer is made part of the recirculating, puri- 

 fying system. Its value has been seriously questioned.' There are two reasons for 

 such installations. The action of the ultra-violet light in purifying the recirculating 

 water may be additive to that of the filter. Furthermore, the residual germicidal ac- 

 tion already referred to may play a part in keeping the pool in good sanitary condi- 

 tion. This action needs extensive and careful investigation before it can be accepted 

 as of any importance. 



BACTERIAL PRODUCTS 



In addition to causing death of the bacterial cell, ultra-violet light may exert a 

 destructive action on products of bacterial metabolism — such as toxins and enzymes — 

 on the various groups of so-called "antibodies" produced in the animal body as the 

 result of the injection of bacteria or their products— such as antitoxins, agglutinins, 

 and lytic substances — or on the lytic material known as bacteriophage. Light may 

 also influence the ability of bacteria to act as antigens by changing the proteins or 

 carbohydrate-like substances in the cell which appear to be responsible for antigenic 

 power or for reactions with antibodies. 



In 191 1 Stessano and Lematte^ stated that while ultra-violet light destroyed the 

 bacterial cell as a living entity, it did not affect the toxins and enzymes in the cell nor 

 did it prevent the power of the cells to cause the production of agglutinins. Irradiation 

 might then be used in place of heat for the production of bacterial vaccines. This has 

 been done but I am not aware that the method has been used extensively. No im- 

 portant studies have been made on the influence of ultra-violet light on the antigenic 

 properties of bacteria. The work of Eberson^ has not been generally accepted. At- 

 tempts have also been made to modify the action of bacteria by the use of sublethal 

 exposures to ultra-violet light. Mme Henri^ claims to have obtained modified strains 

 of the anthrax bacillus, but I cannot find any confirmation of her work. Such effects 

 do not appear to be theoretically impossible. 



Almost nothing has been done on the effect of light on bacterial enzymes. If we 

 assume, and I know nothing against such an assumption, that these enzymes do not 

 differ from those produced by body cells, we can fairly well predict the course of 

 events. Pincussen^ and his co-workers have studied the effect of ultra-violet light 

 on diastase, amylase, trypsin, urease, etc. The results parallel those with living cells. 



' "Swimming Pools and Other Bathing Places," Am. J. Pub. Health, 16, 1186. 1926. 

 ^ Stessano and Lematte: Compt. rend. Acad, de Sci., 152, 623. 1911. 

 ^ Eberson, F.: J. Immunol., 5, 345. 1920. 

 '•Henri, Mme V.: Elec. Rev., 74, 768. 1914. 

 sPincussen, L.: Biochem. Ztschr., 134, 459. 1923. 



