42 David H. Dolley, 



chosen lor their age, the difference is little diminished. As a matter 

 of fact, this is only apparent, for the senile cells here classed are 

 resting cells, — an active senile cell would be classed with activity. 

 There is absolutely no evidence that substances of fatigue excite to 

 activity. 



After having given these results their proper emphasis, the experi- 

 ments on the puppies may be analyzed. The idea in starting these 

 was that such young sucklings would exhibit a comparatively quies- 

 cent cellular state and hence would be particularly adapted for com- 

 parison of possibly moderate degrees of change after experimentation. 

 Though the idea was totally wrong, yet a wide field of possibilities 

 in the study of the development of function and the effect of func- 

 tional usage has been opened up. A brief reference to the table will 

 show that the cells of the whole litter of six (Experiments 13 and 14, 

 23 to 26), at the age of six weeks, average considerably more active 

 than the cells of the " adults. It is also marked in Experiments 29, 

 30 and 30a, which are two months old puppies, and becomes least 

 marked in Experiment 28, a three months old puppy. Outside study 

 as well has convinced us that here is a truth. The cells of young 

 dogs are more labile in reaction than the cells of adults. The same 

 apparent stimulation produces a greater effect and collectively the 

 cells are always more advanced in activity. 



It is obvious that such a condition renders the comparison of 

 the different puppies more difficult and the conclusions, under certain 

 limits of divergence, less sure. Wide variation above the normal 

 average would afford proof of an excitatory effect but a lesser one 

 would be on the same status as in the adult, a matter of individuality. 

 While evidence of any transient initial excitatory effect, which is 

 physiologically indicated, is thus overshadowed, granting that it does go 

 to appreciable anatomical change, fortunately the essential point is 

 definite. As before stated, the transfusion would be demanded to 

 produce a decided effect, corresponding in some measure to the known 

 activity of the donor (Experiment 22). There is no indication of such 

 an effect. On the contrary, analyzing the counts in the first six experi- 

 ments in every way, they come more nearly to being on a common 



