456 Mr. A. J. Walton. Growth of Adult Mammalian 



that in the autogenous plasma (fig. 4) was considerably less than that in 

 the three- day-old plasma, that in the homogenous was greater than that in 

 the three-day-old homogenous plasma and rather less than that in the fresh 

 autogenous. In the case of the testicle taken from animal B, there was 

 again no trace of growth in the plasma from either animal which had been 

 frozen for ten days (fig. 3), but in the three-day-old plasma there was 

 marked growth in the plasma from animal A, which in this case was 

 homogenous (fig. 2), and little or no growth in the plasma taken from 

 anhnal B, which in this case was autogenous. With the fresh plasma 

 there was growth in both series, but that in plasma A, homogenous, was more 

 marked (fig. 1) than that in plasma B but was much less than that in 

 the three-day-old homogenous plasma. These results are shown in the 

 following table : — 





Animal A. 



Animal P>. 





Plasma A. 



Plasma B. 



Plasma A. 



Plasma B. 





Autogenous. 



Homogenous. 



Homogenous. 



Autogenous. 



10 days 



















3 days 



Very good 

 Good 



Slight 

 Fair 



Very good 

 Good 



Slight 

 Fair 



Fresh 











The above experiments showed that, as regards the testicle, growth was not 

 dependent upon any variation in the nature of the cells, for growth was 

 equally good in the series whichever testicle was taken, but it varied directly 

 with the plasmatic medium which was used. The variations in the plasma 

 were not specific to either autogenous or homogenous tissues, for in the 

 experiments given above tissues from both animals grew in the one plasma 

 whether it was autogenous or homogenous, whereas in the other plasma 

 they grew badly in either case. Some plasmata give good growth and 

 others but little, but at present there is not sufficient evidence to show 

 upon what these differences depend. 



The fact that growth was always better in plasma that had been frozen for 

 a certain time, whereas, if kept frozen for a longer period, growth entirely 

 ceased, seemed to show that each plasma contains two substances, one of 

 which inhibits growth and the other which stimulates it. By exposure 

 to freezing for two or three days we may suppose the inhibitory substance 

 is destroyed so that growth is increased. After a longer period, about 

 eight days, the stimulating substance is also destroyed and hence there is 

 no growth. Under normal conditions the stimulating substance is in excess 



