TISSUE CULTURE 349 



Locke Solution : 



NaCl 9-0 gnu. 



KCl 0-42 „ 



CaClg 0-24 „ 



NaHCOg .... 0-20 „ 



Aq. dest 1000-0 c.c. 



For Locke-Lewis solution make up a 15 to 20 per cent, solution of 

 chicken bouillon in Locke solution and add 0-5 per cent, dextrose. 

 Ringer Solution (used for heparin solutions). See page 731. 



781. pH Determination of Salines and Extracts. Phenol red 

 (jjH range 6-8-8-4) is fortunately non-toxic to living cultures and 

 withstands autoclave sterilisation. It is convenient to have 

 ampoules containing about 1 c.c. of 0-5 per cent, sterile aqueous 

 solution in stock. A set of standard buffers are also required for 

 comparing the phenol red coloration of these and the saline 

 solutions or extracts. If the saline is too alkaline add more sterile 

 NaH2P04 solution or bubble sterile CO2 through it. Carrel adds 

 a few drops of phenol red to the mediimi in flask cultures and so 

 controls the jjYL of the culture approximately by adding appro- 

 priate mixtures of CO2 and air to the sealed flask. 



782. Preparation of Plasma. The important factors in pre- 

 paring plasma, apart from complete sterility and sjieed are : — - 



(1) The prevention of contamination of the blood with tissue 

 juices. 



(2) Collecting the blood and later the plasma in contact only 

 with paraffin wax or sterile oils. 



(3) Chilling the blood as soon as possible after its withdrawal. 

 Fowl Plasma. When large quantities are required for routine 



work, bleeding from the carotid artery is to be preferred. Select 

 a cockerel about one year old and starve for twenty-four to thirty- 

 six hours, allowing it plenty of water. Anaesthetise the bird 

 lightly, outside the operating room, and tie it on its back to a 

 dissection board with the ventral surface of the neck conveniently 

 orientated for operation. Remove the feathers from the neck and 

 swab the skin and the remaining feathers with alcohol. Cover 

 the body with a sterile cloth bag or with towels and bring it into 

 the operating room. After making a longitudinal incision in the 

 mid-ventral line of the neck, reflect the skin and clip its edges to 

 sterile towels. Expose the carotid artery on one side only. The 

 vessels lie close together in the mid-line just deep to the fascia 

 covering the anterior neck muscles. First ligature the artery 

 distally with silk or gut and pull it gently forwards into a small 

 loop on which a loose proximal ligature should then be tied. 

 Make a small incision between the two ligatures and immediately 

 wash the cut vessel with sterile saline solution to remove tissue 

 juices. Flood the artery and surrounding neck tissues with 

 sterile olive oil or paraffin. A metal cannula, sterilised in oil, or 



