TISSUE CULTURE 71 



fifty years ago, when Ringer found that a frog's heart removed 

 from the body would beat longer if suspended in a saline solution 

 and still longer if a small amount of calcium chloride were added. 

 On the basis of these experiments, Ringer made the solution which 

 now bears his name. The ingredients and proportions are as 

 follows : 



NaCl 9.0 grams 



KCl . 42 gram 



CaCl2 0.25 gram 



H2O 1,000 cc. 



Ringer's solution was modified for one purpose and another 

 before the days of tissue culture in the strict sense. Ringer 

 himself had tried the addition of other salts. From such experi- 

 ments Locke developed a solution which has been much used in 

 the cultivation of cells and tissues: 



NaCl 9.0 grams 



CaCl2 0.24 gram 



KCl : 0.42 gram 



NaHCOa 0.2 gram 



H2O 1,000 cc. 



A similar solution is that of Tyrode of the following composi- 

 tion, now used in tissue culture: 



NaCl 8.0 grams 



KCl 0.2 gram 



CaCl2 0.2 gram 



MgCla 0.2 gram 



NaHCla 1.0 gram 



NaH2P04 0.5 gram 



Glucose 1.0 gram 



H2O 1,000 cc. 



Fragments of the heart, posterior limb, or any other part of the 

 chick embryo will usually survive in such solutions for a week 

 or more at a temperature of 37.5°C. Pure salt solutions, such 

 as the first two listed, will, if slightly modified {e.g., Pfeffer's solu- 

 tion), serve a normal whole plant quite well, because plants have 

 the ability to manufacture organic food from inorganic material. 

 Animals lack this capacity. Consequently, while cells from 

 body tissues will live for a time in a Ringer solution or even in a 

 simple saline (single-salt) solution, yet cells do not live long, nor 



