MICROPHYTOLOGY 131 



proper fermentation of wine and beer, and all the 

 "diseases" to which these beverages are liable, are due to 

 microbes. The successful development of the flavour of 

 butter and ripening of cheese, the preparation of indigo and 

 the curing of tobacco depend upon the use of the most 

 desirable kinds cf these minute organisms. In agriculture 

 the reduction of nitrogenous manures to a condition in 

 which they can be utilized by crops, and even the fixation 

 of free nitrogen from the air to balance the waste due to the 

 escape of nitrogen into the air and into rivers, is again the 

 work of germs. They also cause certain diseases in plants. 

 Various other processes might be named to show how many 

 different classes are interested in the study of minute 

 organisms, and to explain the participation in it of many 

 besides those who first, and most naturally, undertook it. 

 But there is also another reason. The investigation of 

 bacteria requires very special training in manipulation and 

 staining, as well as in the use of the microscope, and since 

 its importance is most urgent to the students of disease, it 

 naturally follows that they have acquired special skill. 

 Hence the agriculturist, the brewer and the dairyman come 

 to the pathologist for information with regard to the organ- 

 isms which he, better than they, is qualified to examine. 



The study may be divided into (i) methods for isolating 

 and cultivating microbes ; (2) the recognition of the specific 

 organisms which are responsible for commercial operations 

 and for disease, and the elucidation of their life-history ; (3) 

 the discovery of the reasons for their indirect and often 

 disastrous effects, the methods adopted by their hosts to 

 protect themselves against their action, and the plans which 

 may be devised to aid the host in his warfare with the 



germs. 



i. The isolation of bacteria is a problem in gardening on 

 a very small scale. The soils in which they grow best are 

 gelatin, agar (made from a Japanese seaweed, and especially 

 valuable because, unlike gelatin, it remains solid at blood- 



