32 



HISTOLOGY OF MEDICINAL PLANTS 



the flat surface next to the specimen. While cutting the sec- 

 tion, press your arm firmly against your chest, and bend the 

 wrist nearly at right angles to the arm. Push the cutting edge 

 of the microtome toward the body and through the specimen 

 in such a way as to secure as thin a section as possible. Do 

 not expect to obtain nice, thin sections during the first or second 

 trials, but continued practice will enable one to become quite 

 efficient in cutting sections in this manner. 



When the examination of drugs is a daily occurrence, the 

 above method will be found highly satisfactory. 



MACHINE MICROTOMES 



When a number of sections are to be prepared from a given 

 specimen, it is desirable to cut the sections on a machine micro- 

 tome, particularly when the sections are to be prepared for the 

 use of students, in which case they should be as uniform as 

 possible. 



Great care should be exercised in cutting sections with a 

 machine microtome — first, in the selection of the type of the 

 microtome; and secondly, in the style of knife used in cutting. 



For soft tissues embedded in paraffin or collodion, the rotary 

 microtome with vertical knife will give best results. The thick- 

 ness of the specimen is regulated by mechanical means, so that 

 in cutting the sections it is only necessary to turn a crank and 

 remove the specimens from the knife-edge, unless there is a 

 ribbon-carrier attachment. If the sections are being cut from 

 a specimen embedded by the quick paraffin method, it is best 

 to drop the section in a metal cup partly filled with warm water. 

 This will cause the paraffin to straighten out, and the specimen 

 will uncoil. After sufficient specimens have been cut, the 

 cup should be placed in a boiling-water bath until the paraffin 

 surrounding the sections melts and floats on the water. Before 

 removing the specimen from the water-bath, it is advisable to 

 shake the glass vigorously in order to cause as many specimens 

 as possible to settle to the bottom of the cup. The cup is then 

 placed in iced water or set aside until the paraffin has solidified. 

 The cake-like mass is then removed from the cup, and the sec- 

 tions adhering to its under surface are removed by lifting them 

 carefully off with the flat side of the knife and transferring them, 



