880 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Becently Kleinenberg has recommended the use of colophonium 

 instead of Canada balsam. The solution in absolute alcohol is not 

 suitable, as under certain circumstances the finished preparations will 

 show large bundles of. crystals. Turpentine should be used as a 

 solvent ; this, however, has the disadvantage that the preparations dry 

 very slowly. The solution in chloroform seems to answer well, but 

 must be filtered before use. Further experience is required with this 

 medium before its use can be strongly recommended. 



A solution of sandarac in absolute alcohol, which at first appeared 

 to answer well, has not, on further trial, proved satisfactory. 



V. Dissecting. — For the dissection of single organs, fresh animals 

 are generally placed in dilute alcohol, or a weak chromic solution. 

 But the tissues are liable to suffer from maceration in these fluids, and 

 hence, where it is important that the tissues should be well preserved, 

 it is advisable to use picro-sulphuric acid, regardless of the injurious 

 effects of the same on the dissecting instruments. The fluid should 

 be changed as soon as it gets thick and the preparation well washed 

 in alcohol afterwards. The hardening capacity of the picro-sulphuric 

 acid is extremely slight, but may be strengthened by the addition of 

 chromic acid. Preparations thus obtained, and subsequently treated 

 with alcohol, staining fluids, &c, should be transferred to creosote for 

 further dissection, as the transparency induced by this medium will 

 greatly facilitate the work.* 



"VI. Imbedding. — For section-cutting, objects are usually imbedded 

 in paraffin. By low temperature, as in winter, it is necessary to 

 work with a softer paraffin than is required for summer. Instead of 

 softening by an admixture of lard, as generally done, it is better to 

 use a paraffin which becomes soft in summer, on account of its con- 

 taining liquid hydrocarbons, and is preferable to lard as it is not 

 liable to become rancid. 



Preparatory to imbedding, the objects are removed from absolute 

 alcohol t to creosote, clove oil, or chloroform, and left until they 

 become thoroughly saturated. The penetration of the clarifying fluid 

 may, in some cases, be advantageously hastened by warming a little. 

 They are next placed in soft paraffin, heated to about 50° C. over a 

 water bath, and allowed to remain for an hour or so. The soft paraffin 

 is then turned off and replaced by a mixture of hard and soft paraffin, % 

 heated to about 50° C. After remaining for half-an-hour or less in 

 the harder paraffin, kept at a steady temperature, they are ready for 

 imbedding. For this purpose a small paper box may be used; or, 

 much better, a box made of two pieces of type-metal, as used in 

 Professor Leuckart's laboratory. As will be seen from Fig. 162, each 



* In the original paper Dr. Mayer speaks not of creosote, but of oil of cloves. 

 The brittleness which is caused by it is in most cases advantageous, but can 

 easily be reduced by the addition of creosote. The tendency to collect in small 

 drops winch is peculiar to oil of cloves may be counteracted by the addition of 

 oil of bergamot. 



t In many cases a lower grade of alcohol will suffice. 



X The ratio of combination must be determined by experiment, since it will 

 depend on the quality of the paraffin and the temperature ; two parts of hard to 

 one of soft work very well for the winter temperature of Naples. 



