16 PROFESSOR RUTHERrORD. 



overcome these difficulties it is necessary to imbed the tissue 

 so as to support and hold it firm during the section. A con- 

 venient substance wherein to imbed tissues is carrot. Skin, 

 blood-vessels and many other tissues may be readily cut after 

 they have been placed between two slices of carrot ; for 

 hardened tendon, spinal cord, or liver, it is necessary to scrape 

 hole in the carrot, and place the tissue therein. Where the 

 shapeof the tissueisvery irregular, or its structure very delicate, 

 carrot is not suitable ; then the tissue should be imbedded in 

 the following paraffine mixture : Solid paraffine, 5 parts ; sper- 

 maceti, 2 parts ; axunge, 1 part (Ferrier) ; or in a mixture 

 of beeswax and olive oil (equal parts). These substances 

 should be melted at as low a temperature as possible, and 

 poured round the tissue, or for flat portions of tissue — e.g., 

 the retina, flat plates of them may be used, and the 

 tissue laid between them. If the tissue be small, an irregular 

 hole may be scooped in the end of a carrot, the tissue placed 

 in it, and the paraffine mixture or the wax and oil poured 

 round it. The carrot forms an excellent table for the knife to 

 rest and move upon. Tissues to be imbedded in wax or 

 paraffine should be as dry as possible, else the supporting 

 substance will not cling to the tissue. The water may be 

 removed from the surface of the tissue by immersing it for a 

 short time in spirit, and then allowing it to dry. Very deli- 

 cate tissues, such as the softened cochlea, may be imbedded 

 in a strong solution of gum (Strieker). 1. Steep the tissue 

 in absolute alcohol for twenty-four hours. 2. Make a 

 cone of blotting pai)er. o. Put into it a saturated solu- 

 tion of gum. 4. Place the tissue in the gum. 5. Set 

 the cone in absolute alcohol to remove the Avater. 6. Dry 

 it till it is hard enough. 7. Imbed it in paraffine or in 

 carrot, and make sections. In making sections it is diffi- 

 cult to hold the tissue and the knife steady. This dif- 

 ficulty is overcome by using a machine. Such a machine, 

 long used by botanists, has been improved by Mr. Stirling, 

 sub-curator of the Anatomical Museum, Edinburgh, and by 

 the author. (See ' Journ. of Anatomy and Physiology/ 

 May, 1871.) The machine consists of a brass plate or table, 

 having a hole in the centre. The hole communicates with a 

 tube, at the bottom of which is a screw. The tissue is placed 

 in the tube, and the paraffine mixture is poured around it ; or 

 the tissue is imbedded in a cylinder of carrot, previously cut 

 to the size of the tube by means of a cork-cutter. The im- 

 bedded tissue is elevated by the screw, a razor is placed on 

 the brass plate, and pushed by the hand obliquely through 

 the tissue projecting from the hole. The screw is graduated, 



