144 



Journal of Applied Microscopy. 



custom to issue to the student five or six 

 preparations illustrative of the subject 

 assigned for that practicum on a stated 

 evening. For instance, if the liver was 

 the subject that the student was engaged 

 upon, he would be given a preparation 

 showing a single staining of the normal 

 structure, one showing a double staining 

 of the same structure, one showing the 

 vascular areas as mapped out by in- 

 jection processes, and another demon- 

 strating the combined effects of staining 

 and injection; in addition to these, two 

 or three preparations illustrating the 

 same subject (that is, the liver) in com- 

 parative histology. With a class as large 

 as forty students, it is not a difficult 

 matter to prepare fifty or sixty such 

 preparations, fixed upon slides and ready 

 for staining and finishing on the part of 

 the student. The work for an entire 

 class, when the material is at hand, prop- 

 erly embedded, can be thoroughly ac- 

 complished in from two to three hours' 

 time. 



The difficulties experienced in using the 

 albumen and gum methods were these: 

 first, that the sections were with diffi- 

 culty floated out evenly upon the solu- 

 tions, causing overlapping of the sec- 

 tions and interfering with ' a perfect 

 field; secondly, from the amount of stain 

 which the albumen or gum would retain, 

 even when used in the most dilute solu- 

 tion. To overcome this we gradually re- 

 duced the ordinary percentage of the 

 solution from one-half per cent, to one- 

 tenth per cent., and yet met with the 

 same interference on the part of the 

 various staining solutions. It was then 

 suggested to use a purely aqueous solu- 

 tion, which was tried with marked suc- 

 cess. Since that time (about four years 

 ago) distilled water alone has been em- 

 ployed for fixing sections to slides. This 

 overcomes the difficulties previously al- 

 luded to, such as the interference of 

 staining and the smoothness of the sec- 

 tion. For the convenience of the labora- 

 tory workers, who are concerned with the 

 making of a large number of prepara- 

 tions, as many perhaps as four hundred 

 for the demonstration of any single prac- 

 ticum, I would recommend the following 

 process: using the ordinary water pan 

 bath, which will accommodate twenty- 

 four slides, the slides are in the first place 

 thoroughly cleansed from any greasy 

 matter, and this is of the utmost import- 

 ance in order to allow of the even dis- 

 tribution of water upon the slide. The 

 pan is filled with the twenty-four slides, 

 distilled water from an ordinary pipette 

 or dropper is floated upon them, in quan- 

 tity sufficient to accommodate the size 

 of the sections. As fast as the sections 

 are removed from the knife they are 

 placed under the distilled water, and as 



soon as the tray is filled, placed over a 

 water bath in a temperature just under 

 the melting point of the paraffin. This 

 point is of the greatest importance, and 

 must be carefully looked to. If the tem- 

 perature rises above the melting point 

 of the paraffin, the relationship of the 

 tissues will be entirely destroyed, as the 

 paraffin gradually separates them. It 

 should be just sufficient, therefore, to 

 float out the entire tissue and embed- 

 ding mass evenly on the surface of the 

 water, and as soon as this point is 

 reached, the tray should be removed 

 from the bath. It is well not to attempt 

 to arrange the sections symnietrically 

 upon the slides until they have cooled 

 slightly. If done too early, the paraffin, 

 being too soft, will adhere to the needle 

 point or instrument used for the pur- 

 pose, and the work will be very much 

 retarded, but if allowed to cool slightly 

 as many as fifty or one hundred prep- 

 arations can be arranged upon a single 

 slide of sufficient size to accommodate 

 them without any danger of sticking 

 together or being disarranged with the 

 instrument used for arranging. 



As soon as the preparations are ar- 

 ranged in the proper position in which it 

 is desired to retain them for future use, 

 the slide is tilted slightly, the excess of 

 water allowed to drain away and stood 

 up in racks for thorough drying. The 

 only disadvantage in this method of 

 which the writer is aware is that the 

 preparations can not be immediately 

 used, but must be thoroughly dried, in 

 order to insure perfect results. 



The other methods more commonly 

 employed (collodion, for instance) allow 

 of the immediate continuance of the 

 work. The best recommendation of the 

 method here described for work of a 

 serial character, to my mind, is that in 

 the making of a series of about sixteen 

 hundred preparations, every one of which 

 was placed upon a single slide, there was 

 a loss of but two preparations in the en- 

 tire series, not one of them coming off in 

 the various fluids used in their further 

 preparation, such as alcohol, water, 

 stain, decolorizing fluid and mounting 

 fluid; we believe that there is less dis- 

 tortion, less shrinkage or swelling re- 

 sulting from a method of this character 

 than is liable to be the case where the 

 gums or albumens are employed, and 

 as the aim is as far as possible to keep 

 the tissues in a perfectly normal condi- 

 tion and relationship, we should, after 

 many years' experience, recommend this 

 as a most suitable and advantageous 

 method. 



J. Melvin Lamb, M. D. 



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