Journal of Applied Microscopy. 



67 



an advantage, now and then a disad- 

 vantage. Nonstriated muscle tissue, cell 

 body, and nucleus of the cells, stain very 

 readily in methylen blue; so easily, that 

 the injection method may be used with 

 advantage in staining the muscle in the 

 walls of vessels. Connective tissue cells 

 are often very clearly brought out, cell 

 body and processes coming out with a 

 clearness which leaves nothing to be 

 desired. Elastic tissue fibers are now 

 and then stained with as much precision 

 as when stained after Unna's Orcein 

 method. Epithelial cells, especially gob- 

 let cells, and endothelial cells are often 

 stained. 



Definite rules cannot be given. The 

 investigator is advised to vary some- 

 what the time interval between the 

 injection of the methylen blue and the 

 removal of the tissues, in some of the 

 Initial experiments; and usually some 

 time may be hit upon, which in the 

 greatest number of instances leads to 

 the desired result. The method is not 

 an easy one, one often meets with 

 reverses, yet when all has been said, I 

 believe it to be the most trustworthy 

 and most satisfactory method we now 

 have for staining the peripheral nervous 

 system. 



University of Michigan, Ann Arbor, 

 Mich., January, 1898. 



A Combination of the Paraffin and 

 Celloidin Methods of Imbed- 

 ding. 



Ulric Dahlgren, 

 Instructor in Histology, Princeton University. 



Several methods of combination em- 

 bedding in paraffin and celloidin have 

 been described by Kultschizky, Ryder, 

 Ide, Field, and Martin. I have seen or 

 heard described several other similar 

 methods used by Child, McCormick, and 

 others. 



Lee, in his " Vade Mecum," gives but 

 scant description of the methods em- 

 ployed by these workers and does not 

 recommend the process for any but those 

 objects which are too brittle for the plain 

 paraffin method. While not having used 

 extensively any of the methods of the 

 workers mentioned above, the writer has 

 used a combination method, a develop- 

 ment of Dr. McCormick's method, which 

 it is believed is of much wider and more 

 useful application than Lee accords to 

 any similar methods. It helps in cut- 

 ting brittle ova; it enables one to prop- 

 erly imbed the ova and embryos of 

 amphibians which are always delicate 

 to handle and which begin, under the 

 plain paraffin process, to disintegrate 

 after a short time in the water bath. In 



general, it materially decreases shrink- 

 age and minute distortions in any tissues 

 it is used with; it enables the sections 

 to be handled more easily after cutting 

 and in many cases resolves cell outlines 

 and certain achromatic structures. The 

 process is one of extreme simiplicity. 

 The tissue is infiltrated in the usual 

 manner with celloidin, and when it has 

 been finally soaked in a bath of fairly 

 thick celloidin (as thick as would be used 

 for ordinary celloidin embedding), it is 

 placed in a large quantity of pure chloro- 

 form, either with or without any quan- 

 tity of the celloidin adhering to its outer 

 surface. In some cases amphibian gas- 

 trulae were cut out in blocks of celloidin 

 which was already hardened somewhat 

 by evaporation. After remaining for 

 twenty-four hours in the chloroform, the 

 objects are removed to a bath of one- 

 half chloroform and one-half cedar oil. 

 In twenty-four hours they are placed in 

 the water bath in paraffin of the grade 

 that will be finally used to embed them. 

 Several changes are necessary, and more 

 time must be allowed than for tissues 

 embedded by the plain paraffin method. 

 The paraffin will be found to have pene- 

 trated the celloidin itself, and the mass 

 cuts with much less vertical compres- 

 sion than in the case of objects in pure 

 paraffin. 



A little thought and experience will 

 convince one that the method Is a happy 

 one which possesses all the advantages 

 which belong to both the single pro- 

 cesses of which it is a combination. This 

 is particularly true of tissues stained in 

 bulk. It is probably the best way of pre- 

 paring for class use sections of embryos 

 and small animals where three or four 

 or more sections from as many regions 

 must be mounted on a slide. 



A Method of Improving Paraffin 

 for Section-cutting. 



On page 94 of Lee's "Microtomist's 

 Vade-mecum" are statements concern- 

 ing the advantage of old paraffin over 

 that which is new that are doubtless 

 correct. 



The method here given may be a well- 

 known one, but I have not noticed it de- 

 scribed anywhere, and as it has been 

 useful to me, have thought it might be 

 to others. 



It is a matter of common observation 

 that paraffin which has been used for 

 some time, and consequently has been 

 melted often or for a considerable time, 

 is better than at first if kept free from an 

 excess of clearing agents. It has been 

 my experience that the consistency of 

 the paraffin generally furnished by deal- 

 ers in microscopical supplies is much 



