[21] PEESER NATION OF MICEOSCOPIC MATERIALS. 627 



"This method diifers iu some degree from that which Schiefferdecker 

 gives for embedding iu paper boxes. As other observers have remarked, 

 his method frequently gives rise to a great number of air-bubbles iu 

 the embedding mass. Consequent upon the altered manipulations of 

 Professor Thoma, we have to adapt the embedded specimen to a cork for 

 the purpose of cutting. This may be done in the following way : The 

 even surface of the cork is covered by a thick layer of celloidiu solution. 

 This is allowed to dry up perfectly, so as to produce a hard membrane 

 of celloidiu. This is again covered with further celloidin solution. In 

 the mean time the lower surface of the embedding mass is cut even and 

 washed with absolute alcohol, and subsequently moistened with a drop 

 of ether. This moist surface is adapted to the stratum of liquid cel- 

 loidin on the cork, and exposed for a few minutes to the open air. After 

 this the whole is placed in dilute alcohol, which in a few hours will unite 

 the embedding mass solidly with the cork. 



"In a great number of cases it may be regarded as a great advantage 

 of the celloidin that it penetrates the tissues thoroughly, and yet re- 

 mains pellucid, so as to be more or less invisible in the specimen. This 

 quality can be made use of in another direction for the purpose of soak- 

 ing specimens which are too brittle to be cut after hardeuing alone. 

 We may make use of celloidin in a similar way to the gum arable men- 

 tioned above. The minute, normal, and pathological anatomy of the 

 lung in particular will derive great advantage from such a proceeding. 

 Indeed, we are not able to get a perfect idea of the changes produced 

 by pneumonia if we do not by this method or by the following (with 

 paraffiue) prevent the loss of a great part of the exuded substances 

 which in this disease lie loose in the areolar cavities. The study also 

 of micro-organisms in the lung will derive great benefit from the cel- 

 loidin method, and it will be very welcome to many to know that the 

 tissues embedded iu celloidin may be stained with the different fluids, 

 ammoniocarmine, alum-carmine, borax-carmine, hoematoxylin, aniline 

 colors, and various others. The reaction of acids and alkalies, partic- 

 ularly acetic acid and solution of potash is, moreover, not interfered 

 with. And further, we are able to color the object before embedding 

 with all staining fluids which are not soluble, or only little soluble, iu 

 alcohol or ether. 



" After staining and cutting the sections may be mounted in glycerine 

 and various other fluids. Mounting in Canada balsam requires, how- 

 ever, some precautions ou account of the chemical character of the cel- 

 loidin. Absolute alcohol and oil of cloves should be avoided and re- 

 placed by alcohol of 96 per cent,, and by oleum origani. This is, at 

 least the advice of Schiefferdecker, and Professor Thoma has had no 

 occasion to be dissatisfied with the result." 



The embedding mass, consisting of equal parts of chloroform and 

 paraffiue, used first by Biitschli, and which admits of subsequent embed- 

 ding in pure paraffiue, has given such excellent results in my hiyid, that 



