270 VERA DANCHAKOFF 



to be slight, otherwise the shell cracks easily outside the region 

 marked. Splits may be stopped by paraffine and the egg still 

 used. As instruments for sawing, small scalpels used in ophtal- 

 mologie may be recommended, a few jaggs on their edge are 

 often useful. An experienced hand will easily determine the time 

 when the eggshell is passed through. Then the egg is again 

 returned to the incubator. After all the eggs are opened instru- 

 ments for aseptic extraction of organs, (a few scalpels, scissors, 

 forceps and bone cutter), and instruments for grafting, (tissue 

 crusher — it is a syringe with a bolt-bottom, another syringe 

 with divisions of 0.1 gram, and a needle, a fine forceps and two 

 pairs of scissors), are sterilized. 



All the next work has to be done quickly. The organ, asepti- 

 cally extracted, is cut in small pieces and passed through the 

 tissue crusher, the tissue mash is then pulled into the syringe 

 and is ready for grafting. Now egg after egg is taken out of the 

 incubator, the shell window is removed, the shell membrane is 

 lifted by the small forceps and an opening cut out with scissors. 

 The allantois becomes visible and often in earlier stages falls off 

 somewhat from the eggshell. Through the needle 0.1 to 0.2 of the 

 tissue is then pushed in, introducing the tissue if possible under 

 the eggshell at least under the shell membrane. Great care must 

 be taken in grafting eggs in advanced stages, because the allan- 

 tois then bleeds intensely, and the contact of the transplanted 

 tissue with the allantois is removed by the extravasat. No 

 graft usually takes, if the grafted tissue is introduced into the 

 cavity of the allantois or deeper. In these cases the tissue is 

 found floating in the form of a greyish mass, containing numer- 

 ous small grains. 



After the tissue has been implanted on the surface of the al- 

 lantois, the window is closed by the piece of the eggshell with- 

 drawn and the sphts are covered by paraffine. The paraffine 

 of a higher melting degree is preferable, in order to prevent its 

 melting during the following incubation of the eggs. If a local 

 graft is desired any mechanical disturbance should be avoided, 

 otherwise a more diffuse distribution of the grafted tissue is 

 easily obtained. The graft takes more successfully if the egg 



