1893.] MICROSCOPICAL JOURNAL. 75 



Microscopical Technique Applied to Histology. — II. 



[From the French of M. Rene Boneval.] 

 ( Continued from fas^e 40.) 



Imbedding in Paraffin. — Procure a soft paraffin that melts 

 at 4^° C, a harder kind fusible at 55" C, and some fusible at 69°. 

 They all should be homogeneous. With these three itinds, by 

 combinations in different proportions, we may obtain masses fusi- 

 ble at a given temperature. 



The specimen taken from 90° alcohol is placed in absolute alco- 

 hol for 24 hours. When completely dehydrated pour into a test- 

 tube 3 c. c. of absolute alcohol, and fill a small pipette with cedar 

 oil. Introduce the point to the bottom of the test-tube, and let the 

 oil run out slowly. Two layers are thus formed — the upper of 

 alcohol, the lower of cedar oil. Gently introduce the specimen, 

 which remains suspended between the two layers. Penetration 

 is effected very slowly ; some hours after the liquids mingle by 

 diffusion, the specimen falls to the bottom. Transfer it then to 

 cedar oil. 



It is now necessary gradually to replace the oil by paraffin. . . . 

 Fill an iron vessel with water, on which float a plate of cork pierced 

 with holes of different sizes. A spirit-lamp will give a constant 

 temperature, aided by a thermometer in the water. Into each hole 

 in the cork place one of those lead capsules used to cap certain 

 kinds of liquor bottles, turning up the edge to prevent it from fall- 

 ing through. In these capsules we imbed the object, to which 

 we now return. After 34 hours in the cedar oil add to the liquid 

 small fragments of paraffin and heat to about 35° C. The object 

 should remain here for a variable time ; g'eneral rule 5 or 6 hours 

 for an object 2 mm. in diameter. Transfer to the hard paraffin 

 heated to 55°, in one of the lead capsules. Leave it here for 5 or 

 6 hours if it is small ; for 24 hours or even longer if the size is 

 large. While the paraffin is still soft we arrange the object in it ; 

 lift out the lead capsule and cool it by floating the cork on cold 

 water. Tear off' the lead when the paraffin is solid, and from the 

 mass cut out a cube containing the object. 



Imbedding in paraffin demands long and laborious manipula- 

 tions, and alters very delicate structures. It should be used only 

 when large and uniform sections are desired. It is very service- 

 able when used in conjunction with celloidin imbedding. The 

 latter has the advantage of maintaining the organs in place, but 

 does not form hard masses. We obtain the advantages of both 

 methods by combining them. The piece infiltrated with celloidin 

 and hardened in chloroforvi is placed for 34 hours in a mixture 

 of chloroform and paraffin heated to 35° C. Transfer to hard 

 paraffin heated to 55°, and proceed as for imbedding in pure 

 paraffin. 



