Practical Hints. 133 



the case in from one to three weeks, according to the size 

 and hardness, the soft parts should be hardened in alcohol in 

 the manner described above. 



CUTTING SECTIONS. 



The great desideratum in sections of animal tissues, both 

 normal and pathological, are extreme thinness, evenness, and 

 sufficient size to bring into view the different parts of which it 

 is composed. This last point has not, as yet, received sufficient 

 attention from microscopists, especially from those engaged in 

 the study of pathological histology, and yet it is of the great- 

 est importance, for ver}'' frequently a pathological new growth 

 will present different appearances in different parts, and often 

 an erroneous conclusion is arrived at in regard to the nature of 

 the tissue, from the fact that but a small section has been ex- 

 amined. The usual method of cutting sections is by imbedding 

 a small piece of the tissue in paraffin or wax and oil, or by 

 clamping it between two pieces of fresh carrot or boiled liver. 

 When firmly held by the imbedding material, the latter is 

 grasped by the thumb and forefinger of the left hand, and then 

 slices are cut off from the tissue by means of a razor held in 

 the right hand. In this manner, it is true, very thin sections 

 may be made, but they are usually small, and not uniform in 

 thickness. Larger and better sections can be made in a micro- 

 tome, which consists of a well, surrounded by a glass ring, and 

 having a sliding bottom which may be moved up and down by 

 means of a micrometer screw. If such an instrument is to be 

 used, the well is filled with one of the imbedding materials, the 

 best of which I have found to be one pait of mutton tallow to 

 two parts of paraffin; the hardened tissue is suspended in it, 

 and the whole allowed to cool. When cold and stiff the im- 

 bedding material is cut away from the tissue downward, in 

 front and on either side, but left standing behind. This is 

 done to cause the razor or section-knife to pass through the 

 tissue only, and not through the imbedding material before it 

 reaches the tissue. If this precaution is not observed, it will 

 be found nearly impossible to cut a large, even section, on 

 account of the difference between the consistency of the paraf- 

 fin and tallow mixture and the tissue to be cut, and particles 

 of the paraffin adhering to the knife are apt to tear a thin 

 section before it is completely cut off. 



An ordinary razor, one side of which is ground flat, or a 



