INTRODUCTION. 7 



it in rectified spirit. In the guinea-pig the cochlea forms 

 a very evident projection into the tympanum, and is 

 therefore very convenient for enabling the student to see 

 how the cone is to be sliced when sections are to be made. 

 Kill a young guinea-pig, sever the head from the body, 

 disarticulate the lower jaw, open the tympanic bulla, remove 

 the stapes, and prepare the cochlea as above. In a young 

 animal the chromic and spirit fluid alone may suffice to 

 soften the bone, and the chromic and nitric fluid may 

 therefore not be required, or at any rate only for a short 

 time. 



It is very important to place all the above tissues in a 

 cool place. A cellar is best in summer. Protoplasm rapidly 

 undergoes change in even a medium temperature. 



