TISSUE-CULTURE IN VITRO IO5 



experiment and for every stage of the experiment, one obtains 

 every second day a control which in turn will be the originator 

 of a new family of cultures, the biological, chemical, and 

 physical properties of which can be compared at any ulterior 

 date with those of the cultures issued from the fragment sub- 

 mitted to experimentation. It is thus possible during a series 

 of experiments lasting several months and bringing about 

 hereditary modifications of the cells (immunity, for instance), 

 to compare cultures proceeding from successive stages of the 

 experiment. The reader is aware that for the majority of 

 biological experiments it is necessary to have one or two 

 controls on which no experiment has been made. This 

 enables one, by comparison, to appreciate the results obtained. 

 But two animals are never identical, whereas the two parts of 

 a same culture are as identical as possible. 



This is not all. To study the characteristics and properties 

 of certain species of microbes it is necessary to dispose of pure 

 cultures; that is to say, cultures composed of one kind of 

 microbe excluding every other micro-organism. It is quite 

 evident that, when there is a mixture of different microbes, it 

 is impossible to define the function of each species in the 

 lesions and accidents determined on an animal by the culture. 

 Science has no use for anonymity. Its aim, on the contrary, 

 is to discover responsibilities. It would also be impossible to 

 prepare preventive vaccine or curative sera against one of 

 these organisms; in other words, we could not manufacture 

 'specific' vaccines or sera. 



This is equally true of tissue-cultures. To be able to study 

 the cytological and physiological characteristics of a certain 

 species of cells, it is necessary to obtain pure cultures. First, 

 Carrel and then, under his direct guidance, Albert Fischer of 

 Copenhagen, Albert H. Ebeling, Raymond Parker, and one or 

 two others have succeeded in isolating absolutely pure strains 

 of fibroblasts (conjunctive cells), osteoblasts (bone-producing 

 cells), cartilage, epithelium, cancer cells, leucocytes, etc. 

 These strains are generally capable of living indefinitely in 

 vitro while reproducing and conserving all their specific 



