206 



THE MICROSCOPE. 



[October, 



but where the fibre has been torn, the spiral weaving will be 

 manifest. It requires a greater stretch of the imagination to con- 

 ceive such results to be the effect of the alcohol or of the teasing. 

 The original structure of the muscle's substance can only be re- 

 sponsible for the microscopic appearance. 



A Bacteriological Potato-Section Cutter. 



By CHARLES F. DAWSON, M. D., 



WASHINGTON. U. C. 



Several methods of preparing potatoes for a culture medium 

 are now in vogue, each having more or less efficiency, and a 

 variable amount of labor. 



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rif. z. 



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One of the most common methods is the use of a large cork- 

 borer, or apple-corer, to cut a cylinder from the potato. This 

 cylinder of potato is divided diagonally, thus making two prep- 

 arations. Pieces of glass tubing are inserted into the thick ends 

 of the two pieces of potato, and they are placed into ordinary test- 

 tubes and sterilized. The pieces of glass tubing serve to support 

 the potatoes above the level of the condensation water, which al- 

 ways settles into the bottom of the tube. In some instances, 

 specially made culture tubes having a constriction near the bot- 

 tom of the tube are used. The constriction supports the potato, 

 and the condensation water falls into the reservoir thus formed in 

 the bottom of the culture-tube. 



If the potato medium is to be kept for some time, we find that 

 there is a great change in the form of the potato, due to evapora- 



