356 BACTERIA AND DISEASE 



and the opinion held by many of the most noted investigators 

 to-day is, that all diseases are caused each by its specific bac- 

 terium. The great value of this discovery is apparent when 

 we consider it in connection with the prevention and cure of 

 diseases. 



The mode of propagation of all bacteria is by a process of 

 transverse subdivision, not unlike that illustrated in the first 

 chapter of this book. 



3. Warmth and Moisture. All bacteria require for their 

 existence both warmth and moisture, so that neither animal 

 nor vegetable matter can be decomposed at low temperatures 

 or in the absence of moisture. This is well shown by the 

 fact that meat may be kept indefinitely in a frozen state. The 

 finding of the absolutely preserved body of the Mammoth 

 elephant, frozen in the ice of Siberia for thousands of years, 

 is a further illustration of the prevention of decay at low tem- 

 peratures. The preservation of meat by drying proves the 

 absence of decay when no moisture is present. 



4. Yeast and mould are examples of two of the simpler bac- 

 teria which are present in the atmosphere at all times;, each 

 seeks its own field for nourishment and growth. When yeast 

 germs find a liquid containing sugar, a process is set up called 

 fermentation. The yeast germs feeding on the sugar convert this 

 into alcohol and carbonic acid gas, and being thus nourished, 

 rapidly increase in numbers, so that when all the sugar has 

 been consumed, and the process of fermentation has ceased, 

 we shall find a large increase in the yeast. 



Mould exists in many varieties, and may be observed in 

 various colors and modes of growth on decaying vegetable 

 matters. 



5. If we begin now the consideration of the disease-produc- 

 ing bacteria, we are confronted by a field so vast that even an 

 outline description cannot be given in a work of this kind. 

 The three main divisions of bacteria have received the names 

 of micrococci, bacilli, and spirilla. The micrococci comprise 



8. Warmth and moisture ? Illustrate the principle. The Mammoth elephant ? 

 4. Yeast and mould ? Fermentation ? 

 6. The three main di viaious of bacteria ? 



