Shptembee 25, 1908] 



SCIENCE 



393 



that the nerve-cell and nerve-fiber, as parts 

 of one individual (the neuron), must have 

 a common irritability. On the other hand, 

 there is striking- evidence, in LangleyV° 

 experiments on the cross-grafting of effer- 

 ent nerves, that here at least nerve im- 

 pulses are interchangeable and therefore 

 identical in quality. The state of knowl- 

 edge as regards afferent nerves is, however, 

 more favorable to my point of view. For 

 the difficulties that meet the physiologist 

 —especially as regards the nerves of smell 

 and hearing— are so great that it has been 

 found simpler to assume differences in im- 

 pulse-quality, rather than attempt an ex- 

 planation of the facts on the other hypo- 

 thesis." 



On the whole it may be said that, al- 

 thoxigh the trend of physiological opinion 

 is against the general existence of qualita- 

 tive differences in nerve-impulses, yet the 

 question can not be said to be settled 

 either one way or the other. 



Another obvious difficulty is to imagine 

 how within a single cell the engrams or 

 potentialities of a number of actions can 

 be locked up. We can only answer that 

 the nucleus is admittedly very complex in 

 structure. It may be added (but this not 

 an answer) that in this respect it claims 

 no more than its neighbors ; it need not be 

 more complex than Weismann's germ- 

 plasm. One conceivable simplification 

 seems to be in the direction of the pan- 

 genes of De Vries. He imagines that 

 these heritage-units are relatively small in 

 number, and that they produce complex 

 results by combination, not by each being 

 responsible for a minute fraction of the 

 total result.^^ They may be compared to 

 the letters of the alphabet which by com- 



"* Proe. Roy. Soc, 1904, p. 99. Journal of Physi- 

 ology, XXIII., p. 240, and XXXI., p. 365. 



" See Nagel, " Handbuch der Physiologie des 

 Mensohen," III. (1905), pp. 1-15. 



" De Vries, " Intracellular Pangenesis," p. 7. 



bination make an infinity of words.^' 

 Nageli^^ held a similar view. "To under- 

 stand heredity," he wrote, "we do not 

 need a special independent symbol for 

 every difference conditioned by space, 

 time or quality, but a substance which 

 can represent every possible combination 

 of differences by the fitting together of a 

 limited number of elements, and which 

 can be transformed by permutations into 

 other combinations." He applied '^loc. 

 cit., p. 59) the idea of a combination of 

 symbols to the telegraphic quality of his 

 idioplasm. He suggests that as the nerves 

 convey the most varied perceptions of ex- 

 ternal objects to the central nervous sys- 

 tem, and there create a coherent picture, 

 so it is not impossible that the idioplasm 

 may convey a combination of its local 

 alterations to other parts of the organism. 

 Another theory of simplified telegraphy 

 between soma and germ-cell is given by 

 Rignano.^" I regret that the space at my 

 command does not permit me to give a full 

 account of his interesting speculation on 

 somatic inheritance. It resembles the 

 theories of Hering, Butler and Semon in 

 postulating a quality of living things, 

 which is the basis both of memory and in- 

 heritance. But it differs from them in 

 seeking for a physical explanation or 

 model of what is common to the two. He 

 compares the nucleus to an electric accum- 

 ulator which in its discharge gives out the 

 same sort of energy that it has received. 

 How far this is an allowable parallel I am 

 not prepared to say, and in what follows 

 I have given Rignano's results in biologi- 

 cal terms. What interests me is the con- 

 clusion that the impulse conveyed to the 

 nucleus of the germ-ceU is, as far as re- 



'^ I take this comparison from Lotsy's account 

 of De Vries's theory. Lotsy, " Vorlesungen fiber 

 Deszendenztheorien," 1906, I., p. 98. 



^"Niigeli's " Abstammungslehre," 1884, p. 73. 



^° For what is here given I am partly indebted 

 to Signor Rignano's letters. 



