SECTIONAL TRANSACTIONS.— D. 361 



Friday, August 6. 

 7. Joint Meeting with Section I for papers ou Tissue Culture. 



Dr. H. M. Carleton, Prof. Ch. Champy, Dr. H. B. Fell, Mr. E. M. 



WiLMER. 



Prof. Ch. Champy. — The method of tissue culture, first introduced by Ross Harrison 

 and then perfected by Carrel, has become an integral part of cellular biology. There 

 are to-day many different methods for the cultivation of tissues. This is because 

 each one has been evolved with a different aim in view. Cultivation in plasma, i.e. in 

 one of the body's own fluids, is the best technique for the study of certain problems in 

 embryo-mechanics. The addition of embryonic extract facilitates both the isolation of 

 pure strains of cells as well as the prolongation of life i» vitro. Methods involving 

 the use of simple inorganic media are useful for cytological studies, while the use of 

 such media, to which nutritive substances have been added, permits of researches on 

 the nutritional conditions of cells. 



It is particularly important clearly to define certain terms. ' Cultivation ' should 

 only be applied to tissue cultures which show division of cells ; ' survival ' should be 

 used only in the sense of living cells undergoing modification without cell-division 

 (as in the case of nerve-cells). 



It is a pity that the word survival has been applied to tissue cultures in a derogatory 

 sense. The value of a method is proportionate to the scientific value of the results 

 furnished by it. Ross Harrison's fundamental researches on the nerve-cell in vitro 

 ■were only survival experiments. Yet they furnished a result of greater scientific value 

 than have the majority of the experiments on tissue-culture done since then. 



My first researches were intended to verify Carrel's results. From the outset I 

 was struck by the fact that the newly formed tissues were histologically very different 

 from the tissues in the original fragment. As the tissues extirpated from the body 

 multiply, so do they progressively lose their previous specialisation. To this 

 phenomenon I applied the term ' Dedifferentiation.' Kidney-tissue in culture shows 

 a particularly marked example of this phenomenon. Smooth muscle and ovarian and 

 uterine epithelium also show it. 



By ' dedifferentiation,' however, I do not mean that the newly formed cells are 

 totally different ; certain features persist. Nor do such cells lose all potentiality of 

 differentiation ; for instance, connective-tissue cultures, if grafted back into the 

 organism, again form collagen fibres. Another feature of certain tissue-cultures is 

 their resemblance to malignant tumours, for the latter also have dedifferentiated, 

 although they still retain certain of the features of the tissues from which they sprang. 

 An interesting fact in cultures made from adult organs in which mitoses are not 

 present {e.g. kidney, smooth muscle, thyroid and neuroglia) is the abrupt reappearance 

 of mitoses in the cultures. 



The study of regeneration in the living organism appears to show that it is condi- 

 tioned by factors similar to those which operate on the extirpated tissues in vitro. 

 There is also a large field for study, by alternating certain of tlie constituents of the 

 medium, of the nutritional requirements of cells. 



The mutual effects of tissues on each other can also be studied in tissue-cultures. 

 This has already been done with interesting results in the case of epithelium and 

 connective-tissue. And, finally, the fact that cells can be caused to multiply (appar- 

 ently indefinitely) in vitro and that in so doing they come to resemble tumour cells is, 

 to say the least, suggestive. 



Dr. H. B. Fell. — The method of tissue-culture ni vitro is peculiarly favour- 

 able for the experimental study of certain problems of vertebrate embryology. It is 

 especially valuable as a means for investigating the capacity of isolated embryonic 

 organs and fragments of organs for self-differentiation. By incubating an embryonic 

 organ or fragment of organ in a c\ilture-tube containing a relatively large volume of 

 plasma and embrj'o extract, it is possible to study the growth and differentiation of 

 the tissue when it is completely isolated from its normal environment and deprived 

 of all nervous and vascular connections. It has been found that embryonic avian 

 tissue growing under such conditions shows a remarkable capacity for normal differen- 

 tiation, and in favourable specimens exhibits comparatively Uttle cellular degeneration ; 

 growth, however, is greatly retarded and extremely restricted. 



