Staining Animal Sections. 77 



The Rocking Microtome. This machine is made by the 

 Cambridge Scientific Instrument Company. It is only used 

 for specimens infiltrated with paraffin, and it is automatic ; 

 that is to say, it can be set to cut sections of definite thick- 

 ness, and every time the handle is pulled a section is cut, and 

 the specimen is moved forward ready for another. 



Infiltrate the tissue with paraffin in the ordinary way in 

 a pill-box, and when the paraffin has set remove the box 

 and trim the paraffin into a rectangular block. Take care 

 to keep the edges quite parallel, so that they may adhere 

 together as the sections are cut and form a riband. The 

 Cambridge Instrument Company make an apparatus for 

 embedding, called imbedding L's. If these are used perfect 

 rectangular blocks are formed ready for fixing to the brass 

 cap at the end of the arm of the microtome, which is filled 

 with paraffin ; this should be warmed over a spirit-lamp, 

 and the block containing the specimen is to be pressed 

 against the melted paraffin until it adheres firmly. 



LESSON 3. 



STAINING ANIMAL SECTIONS AND MOUNT- 

 ING IN CANADA BALSAM. 



All sections of organs and tissues should be stained with 

 some colouring reagent, so that their structure may be 

 made more apparent. Certain parts of the tissue have a 

 special affinity for the dyes or stain ; they therefore become 

 more deeply tinted, and stand out clearly from the sur- 

 rounding tissues. 



The following staining reagents are the most useful : 

 Borax Carmine. Pure carmine, 1 dram ; liquid am- 

 monia, 2 fluid drams. Dissolve the carmine in the am- 

 monia in a test-tube, with the aid of a little heat if 

 necessary, then add 8 ounces of a saturated solution of 

 borax in distilled water, and filter into a stoppered bottle. 



