476 



On the Variation in the Groivth of Mammalian Tissue in Vitro 

 according to the Age of the Animal. 

 By Albeit J. Walton, M.S., F.B.C.S., M.B., L.R.C.P., B.So. 



(Communicated by Prof. W. Bulloch, F.R.S. Eeceived December 8, 1914.) 

 (From the Bacteriological Department of the London Hospital.) 

 [Plate 15.] 



In a previous communication* it was shown that there was considerable 

 variation in the value, as a culture medium, of plasmata taken from different 

 animals of the same species ; that these plasmata did not vary as to whether 

 they were homogenous or autogenous, but that some plasmata were good 

 media and some were bad. During this investigation certain evidence arose 

 that this difference might in part be due to the age of the animal. 



In the present investigation a series of experiments was carried out to 

 show what was the effect, if any, of the age of the animal upon the plasma 

 as a culture medium, and upon the tissues as regards the power of growth. 

 Carrel, Burrows, Harrison, and Ingebrigtsen have shown in several papers 

 that embryonic tissue tends to grow more rapidly and more vigorously than 

 adult tissue. There appears to have been, however, no work conducted on 

 the characters of the plasma, although it has been frequently assumed that 

 the plasma of the young or embryonic animals makes a more suitable 

 medium than that of adults ; nevertheless it was permissible to believe that 

 the reverse might in fact be true, and that the plasma of young animals is a 

 less suitable medium. It would appear important that this point should be 

 settled, that thereby evidence might be gained as to the controlling influences 

 on the growth of young tissue in vivo. 



Technique. 



The following experiments were carried out entirely with the tissues of 

 rabbits. As far as possible animals were used that had been bred in the 

 laboratory, so that the exact age was known. This was the case with all the 

 young animals. In certain cases, however, adult rabbits were bought of 

 unknown age, but in such cases they were all fully grown and therefore could 

 be used as adult animals. As far as could be judged, they were all over a 

 year old. The technique of Carrel was rigorously adhered to, the tissues 

 being grown in pure plasma so that the characters of the growth might be 



* 'Koy. Soc. Proc.,' B, vol. 87, p. 452 (1914). 



