83 



free I'roiii Ihe surrounding lissue. The wall oT llie l)lood 

 vessel is cleaned with dry gauze and covered with olive oil. 

 If an ai'lcry is used the pari distal to the place selecled 

 for the incision is closed with a ligature and the part cen- 

 tral to the place of incision is closed with a scrresfines. The 

 vessel wall is then opened by a slight cut with a paii' of 

 small scissors and a cannula, which previously has been ste- 

 rilized in olive oil, is inserted inlo the lumen of the vessel. 

 A ligature is then made round the blood vessel to fix the 

 cannula tightly. The serresfines on the central part of the 

 vessel is taken away and the blood now^ flows out of the 

 cannula. The first few c. c. of blood are not collected but 

 then the blood is allowed to flow- down into paraffin- 

 coated tubes, previously cooled at ' C. The tubes are corked 

 and centrifuged for five minutes. The supernatant plasma is 

 removea with pipettes coated with paraffin. The plasma is 

 stored in pai'affin-coaled tubes in an ice-box. In this way 

 the plasma from chickens can be kept fluid for several 

 weeks. 



2. Preparation of the Embryonic Tissue 

 Juice. Fresh fertile eggs are incubated in the usual way 

 at a temperature of about 39 ° C. The air in the incubator 

 is allovveci a certain humidity. Every day the eggs are moved 

 to prevent the embryo keeping the same position all the 

 time. Wher- the eggs have l)een incubated about 1 — 7 days, 

 they arc candled to see if they are good. 



The embryo used for making the extract are usually from 

 7 to 10 days old. The eggs are opened by cracking the 

 shell on the upper quarter of the shell at the broad end. 

 The shell is taken away as a little cap. This part corres- 

 ponds to the air chamber of the egg. The snowy white mem- 

 brane just under the shell is opened with a small sterile 

 forceps and the amnionic sac appears w^ith the rich vas- 

 cular system shining through. With a small pair of scissors 

 this sac is opened and one can now, with an iris forceps, 

 grasp the little embryo around its neck and remove it 



6* 



