78 



MOUNTING AND LABELING. 



? 180. Arranging and Labeling Serial 

 Sections. — In order to determine the mor- 

 phological arrangement of embryos and 

 minute animals where gross dissection is 

 impossible, it has been found of the higbest 

 advantage to make serial sections. These, 

 for convenience of study, should be placed 

 on the slide with the dorsal side pointing 

 toward the top of the slide (i. e. , away from 

 the label). The sections should all be the 

 same side up also. If they are put with the 

 caudal aspect up, then the dorsal side being 

 toward the top of the slide, the various 

 parts of the embryo or animal will have its 

 right and left corresponding with the ob- 

 server. Finally it is almost universally 

 agreed that the sections shall be placed on 

 the slide like columns of figures. 



In histological studies it is also frequently 



Fig. 57.— Example of a slide of serial sections of great advantage to have the sections in 

 labeled for the cabinet. serial order, then an obscure feature in one 



section is frequently made clear by the one following. It is only in the study of 



the individual, isolated, histological elements that serial sections are not necessary 



or at least desirable. 



The label of a slide with serial sections should possess at least the following : 



1. The number of the series. 



2. The thickness of the cover-glass. 



3. The number of the slide in the series. 



4. The name and source of the series. 



5. The number of the first and last section on the slide. 



6. The total thickness of all the sections on the slide.* 



7. The date of making the preparation. 



§ i8i. Cataloging Preparations.— It is believed from personal experience and 

 from the experience of others, that each preparation should be accompanied by a 

 catalog containing at least the following information. Of course when not ap- 

 plicable any of the numbers in the formula may be suppressed, or the order 

 changed : 



* The thickness of all the sections on a slide is easily determined by noting 

 carefully the position of the microtome screw before the first and after the last 

 section for the slide is cut. One can easily measure the amount of elevation of 

 the screw in cutting the sections on a slide, and if the sections are of even thick- 

 ness, the thickness of each section may be determined. The average thickness 

 can be determined in any case. 



