THE MICROSCOPE. 29 



from pre-existing similar beings. The nomenclature, unfortunately, 

 is much confused, each investigator naming according to his fancy. 

 The French school, following Pasteur, make use of the terms vibrios, 

 monads, torulacese, etc. Cohn's classification, according to Dr. Bel- 

 field, is probably the best; however, it needs some improvements. 

 This nomenclature distinguishes the bacteria by form as micrococci, 

 micro-bacteria, bacilli, spirilla. 



The doctor thus defines bacterium: A mass of matter of definite 

 shape and size, possessing .or not possessing motion, of a certain 

 chemical composition, having the power of growth and reproduc- 

 tion. No mass of matter can be said to be bacteria unless it pos- 

 sesses these qualities. 



Even the mycologist cannot determine beyond doubt that a 

 given object is one of the bacteria, except by cultivation outside of 

 the body, thus demonstrating its reproductive power; but just here 

 comes the practical hitch — many objects may come in contact with 

 the particle under examination which might also contain bacteria. 

 The doctor referred to cases showing how mistakes which had been 

 made in the dissection had led to very erroneous conclusions. 



The only means by which an organism in a culture can be 

 shown to be the progeny of that first transplanted, is that it must be 

 observed to proceed from it by continuity of structure: in order so 

 to do we must directly observe it under the microscope. To do so, 

 we must use a solid vehicle for the nutrition and cultivation of the 

 organism. A solution of gelatin, beef extract, peptone, etc., is 

 sterilized, and spread upon a disinfected slide, and allowed to dry; 

 a heated needle is then dipped into the material containing the bac- 

 teria, and drawn lightly over the substance upon the slide, by which 

 a scratch is made, to the edges of which the bacteria adhere; the 

 slides are now to be placed in the incubator. 



By tiiis method we are able to know that the bacterium in the 

 hundredth culture, for example, is structurally the same as the or- 

 ganism taken from the animal which had suffered from the disease 

 in which the original bacterium was found. 



Billroth asserts the presence of bacteria in perfectly healthy ani- 

 mal.-. Koch, Pasteur and Ehrlich have never so detected them. 



Abnormal composition of the blood seemed to favor the de- 

 velopment of some bacteria, after they had gained entrance to the 



