EXPERIMENT STATION BULLETINS 227 



LABORATORY WORK. 



It may seem out of place to introduce into a simple treatise of the fun- 

 damental steps of bacteriology, a description of laboratory methods, yet 

 an explanation will not be necessary if it is borne in mind that it is really 

 a laboratory science; and for a successful interpretation of any article 

 dealing with bacteria, a knowledge of the methods employed is obligatory. 

 There is also another phase of this matter, which enhances the considera- 

 tion of laboratory methods, and which, if kept in view, will lead to much 

 practical good. This is a study of laboratory methods with the direct 

 object of adapting them in, modified forms to every-day life. If careful 

 attention is given in the review, still another feature, accuracy in detail, 

 will be observed in every step of an experiment. Accuracy is indeed the 

 most essential quality to a successful woiker in the laboratory. 



It is a difficult task, even with the best illustrations, to describe appar- 

 atus. Without an idea of the apparatus, laboratory knowledge would be 

 meaningless, and a comprehension of the work would be impossible. A 

 description, therefore, of the apparatus, with a view mainly to state the 

 principle involved, will be undertaken. 



Laboratory work embraces the study of bacteria in all of their biological 

 aspects, which signify their morphology, cultural properties, chemical pro- 

 ducts, and many other associated branches of observation. To accomplish 

 this object it becomes necessary to enter into a consideration of means to 

 an end. To make the subject as simple as possible, topics will be inspected 

 in a light which will not cause much confusion. The complex apparatus 

 will be compared with things already understood. In fact the every-day 

 utensils about the house are embodied largely in bacteriological apparatus 

 which are modified for convenience. These modifications are not essential 

 for an UDderstanding of the principle and may be entirely overlooked. 

 Let us now attend to the laboratory work. 



STERILIZATION. 



From the bacteriological standpoint, sterilization is the process of ren- 

 dering any substance free from bacteria; any way in which this may be 

 done is a means of sterilization. It must not be confused, however, with 

 such terms as Pasteurization or disinfection. Pasteurization refers to the 

 process of reducing the number of bacteria by killing those most suscep- 

 tible to a certain degree of heat; while disinfection is usually limited to 

 pathogenic bacteria, and means either the killing or the reduction of their 

 vitality. 



Several methods are recognized in the accomplishment of sterilization. 

 Because of the extensive application of sterilization to diverse objects and 

 substances, it is readily seen that no method is desirable for all. They all 

 have their particular advantages. Of the three general agents employed, 



