22 



SCIENCE. 



[X. S. Vol. XXI. Xo. 523. 



result at ouee suggests that the mechanism 

 of the increase is dissimilar iu the two 

 cases. For the solution of the problems 

 that are raised by such investigations as 

 those just cited, we need to employ quan- 

 titative methods, and on this topic a word 

 is here in place. 



I\Iicroscopic anatomy and histology, like 

 all the sciences, have passed through a 

 series of jDhases which are as necessarily a 

 part of their history, as birth, growth and 

 maturity are a part of the life history of 

 a mammal. The microscope in its early 

 days enabled Schwann to propound the 

 fruitful theory that the tissues were com- 

 posed of cells. A preliminary survey 

 showed that these cells were different in 

 their form and arrangement in the differ- 

 ent parts of the body, and a still more 

 careful examination with the aid of various 

 dyes or solutions altering the tissues in the 

 differential way gave the basis for yet finer 

 distinctions. This phase in the develop- 

 ment of the science, however, may be fairly 

 compared with qualitative work in chem- 

 istry, where the object is to determine how- 

 many different substances are presented in 

 the sample examined. Naturally, the next 

 step is the introduction of quantitative 

 methods, and we are, therefore, now using 

 the methods of weighing, measuring and 

 counting for the purpose of rendering our 

 notions more precise, and thereby facili- 

 tating accurate comparisons. When em- 

 phasizing this point, we do not, however, 

 forget that hand in hand with this quanti- 

 tative work the qualitative tests have been 

 marvelously refined, and that these neces- 

 sarily form the foundation for quantita- 

 tive work, since all such work must deal 

 with the elements or groups of elements 

 which can be sharply defined, and the basis 

 for their definition is given through quali- 

 tative studies. As progress is made along 

 the.se lines, we appreciate more and more 

 that it is of importance for us to know not 



only how much brain and how much spinal 

 cord by weight normally belong to a given 

 species of animal, but also the quantitative 

 relations of the different groups and classes 

 of elements which compose these parts. 

 AVe are continually asking ourselves how 

 far the range in gross weight of the central 

 nervous system may be dependent on 

 changes in the number of elements in the 

 different divisions or localities, and how 

 far dependent on the mere increase in the 

 bulk of the individual units without any 

 change either in their absolute number or 

 relative size. Work along this line rests, 

 as we know, on the neurone theory, that 

 epoch-making generalization concerning the 

 structure of the nervous system which was 

 put forward by our honored colleague, 

 Professor Waldeyer..* Most of us are 

 aware that, at the moment, this theory is 

 the subject of lively and voluminous dis- 

 cussion, and that Nissl,f for example, urges 

 the inadequacy of the conception on the 

 ground that it does not account for the 

 gray substance in the strict sense. 



No one can fail to appreciate the very 

 great importance of the satisfactory con- 

 clusion of the present dispute, and earn- 

 estly desire that we may obtain conclusive 

 evidence on points involved ; but however 

 the question of the gray matter may be 

 settled, the enormous importance of the 

 neurone conception, and the value of it for 

 the purposes of the microscopic analysis of 

 the iiervoiis system, will remain untouched, 

 while our quantitative determinations ap- 

 plied to the neurone as we now understand 

 it, will still have a permanent vah;e. 



Returning to the questions which are 

 raised by the previously mentioned investi- 

 gations of Dubois, we require in the first 

 instance to determine the number of neu- 



• Waldeyer, Deutsche medicinische Woehen- 

 schrift, 1891. 



t Nissl, ' Die Neuronenlehre und ilire Anhiinger,' 

 1903. 



