1096 SUMMARY OF CURRENT RESEARCHES RELATING TO 



is quite impossible, of course, to lay down any precise rule as to 

 the time required for staining satisfactorily portions of any given 

 organ ; though twenty-four hours' immersion in a 1/2 per cent, solu- 

 tion of hsematoxylin will, in the majority of cases, give satisfactory 

 results, in some instances the object will be rendered too black, and 

 in others will be found not to be stained throughout. The tissues 

 which require the most prolonged staining, when hardened by one 

 method, may become much more rapidly coloured when treated in 

 another way. It will, therefore, be found necessary, in order to 

 insure good specimens of all the organs, to tahe several pieces of each, 

 prepared in different ways, and subject them all to the same process 

 of staining ; or else, taking several pieces of each specimen, to subject 

 each of them to the action of the staining fluid for a different interval. 

 The results obtained by this method excel, in Mr. Haswell's opinion, 

 in the definiteness of the cell-outlines, and the distinctness of the 

 differentiation of the tissues, any that can be obtained ^by any of the 

 ordinary processes of staining capable of being carried out in a class. 

 Imbedding in Paraffin.*— Specimens of animals or of organs 

 stained as above described en hloc, and afterwards treated with bichro- 

 mate of potash, require, after soaking for a few minutes in distilled 

 water, to be treated with strong alcohol for several days — absolute 

 alcohol being used for at least the last two days — in order completely 

 to remove the water with which they have become saturated. As in 

 staining so also in the imbedding, both time and material are saved 

 by preparing a large number of specimens — say twenty or more — at 

 one time. The alcohol is then replaced by chloroform. If the objects 

 are delicate and complicated, this will be very conveniently and 

 thoroughly effected by using some such contrivance as the chloroform- 

 box which Mr. Haswell employs. This is an oblong brass box, 

 divided internally into two compartments by a vertical partition, 

 which does not reach the bottom, but leaves an opening of 3/4 in. 

 Chloroform, with a slight admixture of sulphuric ether, is poured into 

 the box until it rises a little above the lower border of the vertical 

 partition. Absolute alcohol is gently poured by means of a pipette 

 on the surface of the chloroform in one of the compartments ; the 

 objects are placed in this, and, as they become saturated with the 

 chloroform, they sink down until they drift through below the parti- 

 tion into the other compartment, which contains only the mixture of 

 chloroform and ether. From this they can be taken out without dis- 

 turbing the equilibrium of the alcohol and chloroform. Ordinary 

 objects may simply be transferred from absolute alcohol to chloroform, 

 and kept 'in the latter for twenty-four hours, or until saturated. 

 Saturation with paraffin is then effected by the well-known method of 

 Giesbrecht. Mr. Haswell uses a special water-bath, with trough 

 divided into a number of compartments. To ensure a good result, 

 equal parts, by volume, of chloroform and paraf&n (of low melting- 

 point) should be used, and the objects should be left in the bath at the 

 temperature of the melting-point of the soft paraffin for about twenty- 

 four hours. 



* Proc. Linn. Soc. N. S. Wales, x. (1885) pp. 277-8. 



