No. 2.] CHANGES IN NERVE CELLS. 129 



Regrets come always too late ; and so, only after the work 

 had been done, the long, tedious measurements completed, and 

 the results footed up, did I notice how widely, in point of size, 

 the cells of one cat differ from those of another (compare cats 6 

 and 11), and wish that I had weighed the cats. Cats 6 and 

 9 were females, and small. However, the question as to whether 

 the size of animals of a species differ by the size or number of 

 cellular elements, or both, is not entirely germane to our sub- 

 ject. Gaule^ would maintain that for any species the number 

 of cells is a constant, variations of size to be accounted for by 

 size of cells. Such a wide variation in the size of cells as is 

 here seen favors this view. 



Many devices were employed to eliminate the personal equa- 

 tion and obtain mechanical measurements. Three persons un- 

 acquainted with the methods of the research kindly consented 

 to assist in the work of measuring. Even here the differences 

 are too plain to make an absolutely neutral state of mind long 

 possible, since each of the three, before completing the meas- 

 urement of a single set, had noticed that the nuclei in the two 

 ganglia were different. In my own measurements, I was wont, 

 from the first, to throw all thought of the work as completely as 

 possible off my mind, to think about something else, to have an 

 interesting story read aloud. In general, also, all the measure- 

 ments of a series were made before any results were footed up» 

 so that the way they were tending could have no unconscious 

 influence. 



This laborious and time-consuming method of treating the 

 sections has been adopted in order to gain some slight mathe- 

 matical hold directly upon the working of the nerve cell. It is, 

 however, inadequate to express the facts of the case, and it is at 

 best but a poor expression of the amount of change. In the 

 first place, it is impossible to measure accurately the jagged 

 outline of a worked nucleus. Our practice has been to measure 

 well out toward the tips of the irregular points into which the 

 nucleus is prolonged ; and this would tend, evidently, to make 

 the computed, larger than the actual volume. In the second 

 place, the quantities in the tables are averages ; whereas, for 



1 Gaule, Justus, Zahl und Verteilung der Markhaltigen Fasern im Froschriick- 

 enmark. Abhandl. d. Math.-phys. cl. d. k. Sachs. Geselhch. d. Wissensch., Bd. XV., 

 No. 9, pp. 739-780. 1889, Leipzig. 



