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



plasma gave only 75 per cent, positive. The growth was again more extensive 

 in the homogenous plasma. 



Although the above experiments seemed to show that growth was better 

 in homogenous than in autogenous plasma, it was possible that in both cases 

 the autogenous plasma happened to be what one may describe as a bad 

 variety. To solve this question a third experiment was performed three days 

 later than the second experiment. The same two plasmata which were used 

 in the second experiment had been preserved frozen and were used again. 

 They were now both homogenous to the culture tissue and were respectively 

 six and three days old. 



Experiment 3. — The two frozen plasmata described above were used, one 

 of which was six days and the other three days old. Cultures of testicle 

 were made in these and in fresh autogenous plasma under similar conditions. 

 The results were somewhat similar to those of the last two experiments. 

 Growth was much more extensive in the homogenous than in the autogenous 

 plasma, thus at the end of three days there was but slight growth of the 

 tissue in the autogenous plasma and marked growth in the three-day-old 

 homogenous plasma, 100 per cent, of the pieces growing. In the case of the 

 six-day-old homogenous plasma it was seen that the growth was more 

 extensive than in the autogenous plasma but less than in the three-day-old 

 homogenous plasma, only 70 per cent, of the pieces growing. Sub-cultures 

 were made from each set and it was again seen that after a period of three 

 days growth was much more extensive in the homogenous than in the 

 autogenous plasma. In the homogenous plasma mitotic figures were very 

 abundant and very well marked. 



This experiment showed that growth was not better owing to the accidental 

 choice of good homogenous plasmata, for the plasma which in Experiment 2 

 was autogenous and gave but poor growth when used in Experiment 3, where 

 it was homogenous, gave a good growth in 100 per cent, of the trials. 

 Another very interesting fact became apparent. The homogenous plasma 

 used in Experiment 2 when three days old was successful in 100 per cent, of 

 the trials, but when used in Experiment 3, that is when six days old, gave 

 less growth, and even this appeared in only 70 per cent, of the tissues. These 

 results are shown tabulated on p. 455. 



The facts suggested that the variations in growth might be dependent upon 

 the length of time that the plasma had been kept frozen, and further experi- 

 ments were therefore carried out to elucidate tins point. No more sub-cultures 

 were made, however, for it was evident that if the same plasma were used 

 it would not be of the same age and therefore further variants would be 

 introduced. 



