LIFE OUTSIDE OF ORGANISM CARREL AND BURROWS. 575 



drop, similar to those of Harrison ; the cultures in a watch glass filled 

 with plasma ; and the large cultures on the surface of a plate, which 

 can be compared to the plate cultures of bacteria. The technique 

 must be elaborate in its details, in order to obtain results which are 

 uniformty positive. Tissues, especially the higher adult mammalian 

 tissues, are easily killed by drying, chilling, and rough handling dur- 

 ing the preparation of the culture. Bacterial infection is also detri- 

 mental to tissue growth. A rigid asepsis is necessary for the prepara- 

 tion of any tissue culture. The culture must be made in a warm, 

 humid operating room, with the same care and rapidity as a delicate 

 surgical operation. If the method is to give uniform results, not only 

 must the above precautions be closely followed but also the perfect 

 teamwork of well-trained assistants is necessary. 



The plasma is prepared from the blood of the animal whose tissues 

 are to be cultivated or from another animal from the same or from dif- 

 ferent species. The blood is taken from an artery or from a vein. 

 When dogs, cats, chickens, guinea pigs, and rats are used, the carotid 

 artery is ordinarily selected. For human beings the blood is easily ob- 

 tained from one of the superficial veins of the arm. The animal is 

 etherized and the vessel is exposed and dissected from the surround- 

 ing tissue. The wall of the blood vessel is rubbed with dry gauze and 

 covered with olive oil, the circulation is then interrupted by a serre 

 fine, the vessel wall is opened laterally, and a glass cannula previously 

 sterilized in olive oil is inserted into the lumen of the vessel. It is also 

 possible to use a needle sterilized in olive oil and inserted through the 

 skin into the vein. The blood is collected in small tubes, carefully 

 coated with paraffin, which have been previously cooled at 0° C. The 

 tubes are immediately corked, placed in large tubes filled with ice, 

 centrifugalized for five minutes, and deposited in a small ice box at 

 0° C. The supernatant plasma is removed with pipettes coated with 

 paraffin. It is generally used immediately, but it can be preserved 

 for some time in a fluid condition if it is kept at a low temperature. 

 Artificial media are also employed. They are composed of agar, 

 glucose, and salts under proper concentration. We used also the me- 

 dium described by Lewis and composed of bouillon, agar, and Ringer 

 solution. 



The tissues used for cultures must be in normal condition. They 

 are best if taken directly from the living animal or from an animal 

 soon after death. With a cataract knife and a fine needle, a small 

 fragment of tissue is dissected from the animal and placed on a glass 

 plate. This piece of tissue is rapidly cut into small pieces about the 

 size of a millet seed and transferred on the point of a needle to the 

 surface of a cover glass. For the large cultures, the tissue is cut into 

 small pieces with sharp scissors, or, what is still better, into thin, 

 broader pieces with a razor. It must be remembered that Christiana 



