390 



METHODS. 



mend for embryological use especially two forms of microtome made by Messrs. 

 Bausch & Lomb, of Rochester, N. Y., and designated by them as the "precision" 

 and " rotary" microtomes. 



The precision microtome (Fig. 261) consists, first, of an upper square form 

 upon which the knife may be clamped in any desired position; second, of two 

 horizontal ways upon which moves the carriage which bears the object-holder; 

 and, third, of a micrometer screw with an automatic feeding contrivance on the 

 under side of the movable carriage. The construction is very solid and great 

 rigidity of the parts is secured. The microtome may be used for either paraffin 

 or celloidin cutting. According to the author's experience, this microtome con- 

 siderably surpasses all other types in the accuracy of the work which may be done 



FIG. 262. THE AUTOMATIC ROTARY MICROTOME. 



with it. The rotary microtome was originally made in Germany, and various 

 patterns have been put upon the market by German, French, English, and Amer- 

 ican manufacturers. The new pattern recently introduced by Messrs. Bausch & 

 Lomb embodies a considerable number of improvements, which render the instru- 

 ment (Fig. 262) very desirable for general laboratory use. It works with accuracy, 

 is very easy to manipulate, and cuts sections with extreme rapidity. It is adapted 

 only for paraffin work. For the general use of students, in elementary courses 

 especially, this microtome is to be preferred to the " precision," as it requires 

 less care and works more rapidly. A single rotary microtome will be found 

 sufficient for a class of from twenty to thirty students in embryology. 



