MANIFESTED LIFE OF TISSUES OUTSIDE OF THE 



ORGANISM. 



By Alexis Carrel and Montrose T. Burrows. 



(From the Laboratories of the Rockefeller Institute for Medical Research, New York.) 



I. INTRODUCTION. 



Fragments of tissues and organs of mammals and other animals 

 can be kept outside of the organism in a condition of manifested life, 

 when they are placed under certain conditions in a proper culture 

 medium. Their life is essentially characterized by an active growth 

 of the cells from the original fragment into the medium where they 

 undergo direct or indirect division. These cells cover a wide area of 

 the medium, and are often very densely packed. They gi'ow during 

 a period of time which varies from 5 or G days to more than 20 

 days, without any evidence of necrobiosis. The cells which have 

 wandered into or have been born in the plasmatic medium can be 

 transplanted into a new medium and produce a very luxuriant 

 generation of cells. A culture of tumor transplanted into the body 

 of an animal can take and gi'ow rapidly. 



The idea of cultivating tissues as previously defined is far from 

 being new. Man}' experimenters have already thought of the pos- 

 sibility of growing tissues outside of the body, and several have 

 attempted to develop adequate method for it. In 1897 Leo Loeb 

 thought that the culture of tissues in an artificial medium outside of 

 the body was possible, and stated that he had found a method for 

 accomplishing it. But the technique and the results of his experi- 

 ments have not been published. In 1907 Harrison demonstrated in 

 a series of splendid experiments, made in the anatomical dei:)artment 

 of Johns Hopkins University, that embryonic tissue of the frog, 

 transplanted into coagulable lymph, will develop normally. The 

 central nervous system of a frog embryo, covered Avith fluid from 

 the lymph sac of an adult frog, produced long nerve fibers. These 

 experiments demonstrated that the nerve fibers are really an out- 

 growth from a central neurone. But they demonstrated also a very 

 much more important fact, the possibility of growing tissue outside 



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