I. 



Introduction. Bacteria or Schizomycetes and Fungi. 

 Structure of the Bacterium-cell (1). 



THE purpose of these lectures is to give some account of the 

 present state of our knowledge respecting the objects included 

 under the name of Bacteria. It is unnecessary to enlarge upon 

 the manifold interest attaching to these organisms at a time when 

 the statement urged daily on the educated public does not fall far 

 short of saying, that a large part of all health and disease in the 

 world is dependent on Bacteria. If we are therefore spared that 

 customary portion of the introduction to a lecture which seeks 

 to impress the hearer with the importance of the subject, it be- 

 comes the more necessary to give prominence from the first to 

 the reverse side of the question ; that is to say, to call special 

 attention to the fact, that the problem presented to us can only 

 be solved by quiet scientific examination from every possible 

 point of view of the objects under consideration; and a study of 

 this kind is dry rather than exciting, or to use a common ex- 

 pression, interesting. But this should not deter any one who 

 is really desirous of acquiring some knowledge of our subject. 



The order of our remarks will follow the natural arrangement 

 .of the subject before us; and our first task therefore will be to 

 ''enquire what Bacteria are ; in other words, to make ourselves 

 acquainted with their conformation, their structure, their de- 

 velopment, and their origin in connection with their development. 

 Next, we have to enquire what they do, what good and what 



