METHODS OF RECONSTRUCTION. 385 



7: Wash thoroughly in water to remove the iron solution, no trace of which 

 can be left without ruining the specimen. (Unless the washing is very thorough, 

 the sections will gradually fade out after the final mounting.) 



8. Dehydrate with alcohol and mount at once in damar. 



8. MALLORY'S TRIPLE CONNECTIVE-TISSUE STAIN. 



Formula I: Acid fuchsine i . o gin. 



Distilled water 1000 . o c.c. 



II: Distilled water 100.0 c.c. 



Phosphomolybdic acid, to be added before other ingredients i . o gm. 



Aniline blue, soluble in water 0.5 gm. 



Orange G 2.0 gm. 



1. Preserve in corrosive sublimate or Zenker's fluid. 



2. Stain the sections in the fuchsine solution one to three minutes. 



3. Wash in water very quickly. 



4. Place in the phosphomolybdic solution two to twenty minutes. 



5. Wash off excess stain in water. 



6. Dehydrate in 95 per cent alcohol and mount in damar. 



This method gives a perfect differential stain of connective-tissue fibrils, and it 

 is to be used whenever the fibrils are to be especially studied. 



Methods of Reconstruction. 



It is often important to obtain definite plastic conceptions of the anatomy 

 of embryos or parts of embryos too small for dissection. To secure these in the 

 best form, it is necessary to reconstruct either drawings or models from sections. 

 The methods employed for these two forms of reconstruction, being different, must 

 be described separately. 



Reconstruction of Drawings from Sections. To make these reconstructions 

 satisfactory, it is indispensable to have an accurate outline of the embryo repre- 

 senting it in the point of view to be used for the reconstruction and enlarged to 

 the precise scale upon which the reconstruction is to be made. This drawing 

 must, of course, be made before the embryo is imbedded and sectioned. It is 

 further necessary to know accurately the plane of the sections and their thickness, 

 and, finally, the total number of sections in the series must be counted. A con- 

 venient scale for the reconstruction of the anatomy of mammalian embryos is a 

 magnification of from 15 to 30 diameters. 



Let us suppose that a pig of 12 mm. has been drawn in a side view magnified 

 20 diameters; that the embryo has been cut into 900 transverse sections and the 

 approximate plane of the sections is known. It may be more exactly determined 

 by the study of the sections themselves; for instance, it may be determined 

 what section is the last to pass through the surface of the head in the region of the 

 fore-brain and the last to pass through the border of the anterior limb. Then it 



