78 IMBEDDING 



Amphibia or the amnion from embryos of higher vertebrates. 

 The four corners of the skin can now be gathered up and twisted 

 together with the aid of forceps, and transferred to the higher 

 grades of alcohol which will quickly harden the skin so that it 

 will not untwist. The skin with the contained material can now 

 be dehydrated, stained with eosin if desired, cleared and imbedded 

 in the ordinary way. Painter used this method in Dr. Boveri's 

 laboratory. 



A method which Gatenby uses for small objects and which 

 originated probably on the Continent, is to sharpen a rod rather 

 bigger than a lead pencil. Silver foil from cigarette packets is 

 pressed over the end to form a cone. These cones have smooth 

 sides and the objects fall to the bottom. The entire dehydration 

 and imbedding process is carried out in the cone (propped up 

 in a small Stender dish), the liquids being gently sucked out with a 

 pipette. When cooled the tip of the paraffin block containing the 

 objects is re-imbedded in a block of cold wax, in which a hole has 

 been made with a hot wire. 



For imbedding verij small objects in this way certain precautions may 

 be necessary in order not to lose them. Samter {Zeit. wiss. Mik., xi, 

 1894, p. 469) saturates small unstained objects with paraffin that' has 

 previously been strongly coloured with alkanna extract, and then 

 imbeds them in pure paraffin. Rhumbler (ibid., xii, 1895, p. 312, and 

 xni, 1896, p. 303) stains previously the objects themselves with eosin 

 dissolved in strong alcohol, and removes the stain from the sections with 

 weak alcohol. See also ibid., xiii, p. 200, a paper by Schydlowski • 

 and in Zeit. wiss. Zool., Iviii, 1897, p. 144, a process of Borgert. 



BoRGERT [Zeit. wiss. Zool., Iviii, 1897, p. 144) allows paraffin to 

 solidify in a watch-glass, bores a hole in it, and places the objects in the 

 hole with a little benzol, and puts the whole for a short time into a stove. 



A watch-glass provided at the bottom with a groove or trough, in 

 which small objects may be made to collect, is described by Lefev're 

 Joimi. App. Mic, V, 1902, p. 280 (see Journ. Roy. Mic. Soc., 1903, 

 p. 233). 



Lauterborn {Zeit. wiss. Zool., lix, 1895, p. 170) brings the objects 

 through chloroform into paraffin in a small glass tube, and after cooling 

 breaks the tube and so obtains a cylinder of paraffin with the objects 

 ready for cutting. 



Hoyer {Arch. mik. Anat., liv, 1899, p. 98) performs all the operations 

 in a glass cylinder (5 cm. long and 7 mm. wide), open at both ends, but 

 haying a piece of moist parchment paper tied over one of the openings. 

 It is then not necessary to break the cylinder ; by removing the parch- 

 ment paper the paraffin can be pushed out of it in the shape of a cylinder 

 containing the objects imbedded at one end of it. 



Mayer {Zeit. wiss. Mikr., xxiv, 1907, p. 130) takes the gelatin capsules 

 used by chemists : after cooling in water the gelatin swells and is easily 

 removed. 



Meves (Arch. mikr. Anat., Ixxx, Abth. ii, 1912, p. 85) employs wedge- 

 shaped capsules made by G. Pohl, Schonbaum, Bez, Dantzig. 



