APPENDIX. 637 



6. Delafield's or Weigert's haematoxylin, several minutes. 



7. Water (to wash). 



8. Water acidulated with HC1 (6 drops HC1 to 50 c.c. water) until tissues appear gray. 



9. Water made slightly alkaline with ammonia. 



10. Water, several changes. 



11. Alcohol, 80 per cent. 



12. Eosin solution until tissues are pink. 



13. Alcohol, 95 per cent. 



14. Absolute alcohol, or carbol-xylol. 



15. Xylol, two successive baths. 



16. Mount in xylol-damar. 



Staining with Heidenhain's hcematoxylin. This can be done with either paraffin or celloi- 

 din sections. The following is the method pursued for paraffin sections. Starting with 

 sections mounted on slides from which the paraffin has not been dissolved, transfer to 



i, 2, 3, 4, 5, as given in the preceding table. 



6. Ammonium sulphate of iron, 2.5 per cent, aqueous solution, 12 to 24 hours. 



7. Water (to wash). 



8. Haematoxylin, i per cent, solution (as stated on p. 636), 6 to 12 hours. 



9. Water (to wash). 



10. Ammonium sulphate of iron (as above) until tissues appear gray. It is best to 

 examine the tissues under the microscope from time to time. 



11. Water, several changes. 



12. Alcohol, 80 per cent. 



13. Alcohol, 95 per cent. 



14. Absolute alcohol or carbol-xylol. 



15. Xylol, two successive baths. 



16. Mount in xylol-damar. 



VIII. METHODS OF RECONSTRUCTION. 



Graphic reconstructions. Making reconstructions of this kind consists o" plotting out on 

 paper magnified representations of structures from a series of sections. Serial sections are 

 of course necessary, and the thickness of the sections must be known. A camera lucida must 

 be used and some given magnification chosen and adhered to for a particular reconstruction. 



Suppose, for a simple example, that a reconstruction of the stomach of an embryo is to 

 be made. First determine the desired magnification. Then, with a camera lucida, draw on 

 a sheet of paper an outline of a section of the stomach at its cephalic end, and, still keeping 

 the paper in exactly the same position, draw a line to represent the median line of the section. 

 On a sheet of drawing paper, upon which a straight line has been drawn to represent the 

 median line of the section (sagittal plane of the embryo), measure off the distance, as indicated 

 in the camera lucida sketch, of each edge of the stomach from the median line and mark 

 with a dot. 



Make the same kind of a camera lucida sketch from the next succeeding section. Plot 

 this on the drawing paper as in the preceding case, putting the dots below, or, so to speak, 

 caudal to the first dots at a distance equal to the thickness of the section multiplied by the 

 magnification. 



Pursue the same method with successive sections, and then connect the dots that rep- 

 resent the edge of the stomach in the sections with a continuous line. The line, of course, 

 represents the outline of the stomach, and, if the plotting has been properly done, it will 



