246 THE AMERICAN MONTHLY [October, 



sued in making artificial cultures of different disease germs, and 

 exhibited various colonies in different degrees of development. 

 A suitable medium for the rapid growth of these colonies is found 

 in a preparation of meat juice and gelatine; another in bouillon 

 and agar (a product of an Indian sea weed, Gelid him splni- 

 fortne). To either of these is added a certain percentage of pep- 

 tone and, for some purposes, glycerine. It was shown what pre- 

 cautions were necessary to prevent the introduction of foreign 

 germs from the air ; how every article used had to be completely 

 sterilized before the germ sought to be cultivated was introduced. 

 The tubes are then placed in an oven which has an automatic 

 regulator of the heat, and kept. at a perfectly uniform temperature 

 for sucli time as may be necessary for the delevopment of the 

 germs. 



Some bacteria make gelatine fluid ; some grow in the presence, 

 others in the absence of air; some require acid, others alkaline 

 media ; some grow only in the presence of glycerine or sugar. 

 There are differences in the color, in the manner of the formation 

 of colonies, in the microscopic appearances and in the effects 

 when thrown into the system as shown in the lower animals. It 

 is by taking advantage of these and other peculiarities that we are 

 enabled to make the differentiating or qualitative bacteriological 

 analysis. 



Among the bacteria which have been most carefully worked 

 out, and which are most dangerous to mankind, the speaker 

 mentioned the bacillus of anthrax, the bacillus of typhoid fever, 

 and the spirillum of Asiatic cholera. It is possible for all these 

 to be carried in the water supply. It may be asked, if there can 

 be so many germs in water, why are not all affected ? The an- 

 swer is easy. Many of the germs are entirely innocent, just as 

 many plants are. Of the remainder, many are destroyed by the 

 various processes of digestion. 



The special apparatus and the methods of procedure for the ex- 

 amination of germs in air, in earth and in food meat were fully 

 described and commented on. The bacteriologist, by means of 

 the knowledge at his command, is in a position to settle certain 

 questions of public hygiene which are pi'actically guesswork with- 

 out his aid. A case was recently reported by Dr. Munn, of Den- 

 ver, where pleuro-pneumonia and tuberculosis occurring in cows 

 had been passed by officials in Kansas City who were not bacte- 

 riologists. In Berlin this inspection of meat by bacteriological 

 methods is so strictly carried out that no diseased cows are now 

 presented for slaughter, and one can buy meat in the shops and 

 be sure he is not taking in tuberculosis at the same time, 



In nothing, perhaps, can bacteriology be of such practical value 

 to a community as in the investigation and regulation of water 

 supplies. As a city, San Francisco is blessed with a naturally 

 good supply. All through our State are wells, each supplying 

 water to one or more families, but contaminated by sewage and 



