72 



Journal of Applied Microscopy. 



hours to a mixture of equal parts of 

 alcohol and ether. Then they go into 

 the thin celloidin solution, where they 

 remain for from twenty-four hours to 

 several days, depending on the size and 

 density of the pieces to be imbedded. 

 The pieces of tissue are then transferred 

 to the thick celloidin solution, where 

 they again remain for from twenty-four 

 hours to several days. The hardening of 

 the celloidin may now be obtained in one 

 of two ways' 



(a) A sufficient quantity of the stock or 

 thick celloidin solution to cover well the 

 tissues to be imbedded, is poured into a 

 flat dish, large enough to allow the ar- 

 ranging of the pieces to be imbedded on 

 its bottom, and leave a space of about 

 one-fourth of an inch between con- 

 tiguous pieces. The dish is then covered, 

 not too tightly, and set aside, to allow 

 the ether and alcohol to evaporate. In 

 one to two days the celloidin is usually 

 hard enough to cut into small blocks, 

 each block containing a piece of the im- 

 bedded tissue. The blocks of celloidin 

 are now further hardened by placing 

 them in 80% alcohol. A stay of several 

 hours in this alcohol is usually suffi- 

 cient to give them the hardness required 

 for section cutting. After the celloidin 

 pieces have obtained the right degree 

 of hardness they are to be stuck to small 

 pieces of pine wood so that they may be 

 clamped into the microtome. This is 

 done in the following way: A piece of 

 celloidin containing a piece of tissue is 

 trimmed with a sharp knife, so that only 

 a rim of celloidin, about one-twelfth of 

 an inch in thickness, surrounds the 

 piece of tissue. It is now placed for a 

 few moments in the ether and alcohol 

 solution. This is to soften the surfaces 

 of the celloidin somewhat. One end of a 

 small pine block, about one inch long, 

 the cut end of which has a surface area 

 slightly larger than the celloidin block, 

 is dipped in the thick celloidin solution. 

 The celloidin block is now taken from 

 the ether and alcohol solution and 

 pressed against the end of the pine block, 

 which has been coated with the hard 

 celloidin. The whole is now set aside for 

 a little while, to allow the celloidin to 

 harden slightly, and is then placed in 

 80% alcohol. In the alcohol it may re- 

 main irdefinitely; it may, however, be 

 used for cutting as soon as it again be- 

 comes hard. 



(b) The piece of tissue to be imbedded 

 may be mounted at once on a pine block 

 from the thick celloidin solution, by 

 pouring a small amount of thick celloidin 

 over one end of the pine block and plac- 

 ing the piece of tissue from the thick 

 celloidin solution onto the layer of cel- 

 loidin on the block of wood. In three to 

 four minutes, a layer of the thick cel- 



loidin solution is poured over the piece 

 of tissue and the end of the block of 

 wood. It may be necessary to do this 

 several times, if the piece of tissue is 

 large or of irregular shape. The block 

 is now set aside for five minutes and is 

 then placed in 80% alcohol, where it re- 

 mains until the celloidin is hard or until 

 it is desired to cut sections. 



As to the choice of the method to be 

 used: In a general way it may be stated 

 that, since the celloidin method is much 

 easier, needs less apparatus, and answers 

 the purpose where it is not necessary to 

 make very thin sections, it may be 

 recommended in preference to the par- 

 affin method for general use in the diag- 

 nostic work which a physician may be 

 called upon to do. 



If a paraffin bath which can be prop- 

 erly regulated is at hand, and where it is 

 desirable to have especially thin sec- 

 tions, the paraffin method is, in my opin- 

 ion, always to be preferred. 



University of Michigan. 

 ( To he Continued. ) 



A Method of Preserving Culture 



Media. 



Every bacteriologist and every one 

 who has occasion for the constant use of 

 sterilized culture media will welcome any 

 means that succeeds in shortening the 

 labor necessary in their preparation. 

 One of the most onerous parts of the 

 work is the necessity of filling fresh 

 tubes at frequent intervals. If the 

 tubes could be filled in large numbers 

 and be kept unaltered for a long time, 

 much trouble would be avoided. 



Culture media do not keep well in 

 tubes in a dry place because the con- 

 tinual evaporation soon changes their 

 composition, nor in a moist place because 

 mold spores will almost invariably find 

 their way to the cotton and will grow 

 through it if it is damp. 



The method suggested here overcomes 

 both of these difficulties. It consists 

 essentially of the use of a second plug of 

 antiseptic cotton, and is put in practice 

 as follows: 



The test tubes are cleaned and plugged 

 in the ordinary way, except that a cotton 

 plug of only half the usual length is 

 used. They are then sterilized in the 

 hot-air sterilizer and filled. Immediately 

 after filling, the cotton plug is pushed 

 into the tube half an inch below the top 

 and a plug of antiseptic cotton put over 

 it. The tubes are then sterilized in the 

 usual, way. After thorough sterilization 

 the tubes may be closed with a rubber 

 cap or put in closed glass vessels to pre- 

 vent evaporation. Ordinary fruit jars 



