/< 



X. 1 TURE 



[November 23, 1905 



on recognisable geological factors, namely, the wearing 

 out of the chasm of the Zambesi and the retrocession of 

 its falls, we have an advance in our positive knowledge as 

 to thi remote age of the Palaeolithic stone implement beds 

 oi South Africa. 11. W. Feildei* 



Terminology in Electrophysiology. 



Taking the diagram given by Dr. Fraser Harris (p. 5), 

 all writers will agree with him that A is positive plate 

 .hiiI negative pole, and 1 believe that the use of the word 

 " zincative " has gone some wa\ to promoting this agree- 

 ment. 



Dr. Harris goes on to say that no loophole for confusion 

 could l)r left if the qualifying words externally or internally 

 were added, by stating, e.g., that A is internally electro- 

 positive to B and externally electronegative to B. 



I find three objections to this suggested clarification : — 

 (1) Tin expressions thus qualified are .cumbrous, and must 

 infallibly become abbreviated in current language by 

 omission of the qualifying words. 



(2) The expression " externally electronegative " contra- 

 dicts the conventional use of the word " electronegative " 

 which is attached to the plate and not to the pole. 



, I lure is no provision for the complementary qualifi- 

 cation to denote that a tissue is capable of being aroused 

 to electromotive action, i.e. capable of being rendered 

 zincative, i.e. zincable. 



I freely admit that this convenient jargon offends the 

 ear while arousing the understanding. I will gladly bury 

 the words " zincative " and " zincable " when they have 

 fully served their purpose as danger-signals that confusion 

 is possible ; but until we have agreed that active tissue 

 shall be called " externally or galvanometrically negative " 

 or "internally electropositive" I do not think loopholes 

 lor confusion have been closed. 1 should be satisfied with 

 the old external word " negative " if it did not involve the 

 conception of an internal " propagation of a wave of 

 negativity," and the occasional misstatement that a wave 

 of electronegativity is propagated through nerve and muscle. 

 I should be glad to say that A is electropositive 10 B il 

 I were not convinced that the prefix " electro " would be 

 occasionally dropped to the further confusion of the reader 

 accustomed to be told that A was (externally) ncgali\. :. 



So that, en attendant mieux, in order that there may be 

 no confusion as to my own meaning that A is externally 

 negative and internally positive, I say that A is like zinc 

 or zincative. The parable, if there be parable, is intended 

 to point out and avoid a confusion, but there appears to 

 be an unfortunate tendency to confuse an indication of 

 confusion with an introduction of confusion. 



The physicist does not help us much. When he has 

 appreciated the ambiguity of our physiological language, 

 which is of physical origin, he supposes it to be no more 

 than another case of the ambiguity familiar to us in the 

 naming of accumulator poles, where, in order to avoid the 

 perplexities that would arise from calling the same plate 

 positive during charge and negative dining discharge, the 

 convention has become accepted always to call positive 

 the plate that is connected with the positive pole of the 

 charging battery or dynamo. 



Our trouble is that there is among physiologists no 

 accepted clear convention analogous with this convenient 

 custom of miscalling the positive plate of an accumulator 

 in a perfectly intelligible manner. Therefore again, when 

 it seems particularly desirable to indicate seat of activity 

 and direction of current internally as well as externally 

 I still say " zincative " in order that there may be no 

 mistake of meaning. A. D. Waller. 



Both Dr. Harris (p. 5) and Prof. MacDonald (p. 28) 

 somewhat misrepresent the use by physicists of the signs 

 + and — . As applied to a closed circuit they are purely 

 relative, each point being simultaneously positive to all 

 points on one side of it and negative to all those on the 

 other. The confusion arises from the fact that terms 

 belonging properly to electrostatics were adopted long ago 

 in describing the phenomena of the galvanic battery. 



It is impossible to define direction in a circle — or any 

 closed circuit — with less than four points — one lying in a 



NO. 1882, VOL. 73] 



different plane from the other three. In a circle drawn on 

 paper, one of these is given, namely, the position of the 

 observer behind or in front of the paper. If we put two 

 others on the- 1 irele there is still ambiguity, for we may 

 go from + to — in either direction, as in the armature 

 coils of a dynamo ; but with the use of three symbols the 

 ambiguity vanishes. Thus abc, oca, cab indicate one direc- 

 tion, and cba, acb, bac indicate the other. As with formula.' 

 containing an asymmetric carbon, the enantiomorph is 

 given by turning the diagram over. 



In diagrams of electric circuits some portion of the 

 apparatus, either the source of E.M.F. or the place where 

 it is being used, is tacitly taken as the third symbol, and 

 the signs + and — put on either side of it to indicate 

 which way the current flows. Dr. Waller's word 

 "zincative," to anyone who knows how zinc behaves, 

 indicates without possibility of error the direction of the 

 current across the region that generates it, and the elec- 

 trically-minded student may trace its 1 ourse thence by 

 arrows, remembering that while the circuit is closed the 

 tail of each arrow is positive to its head, but directly the 

 circuit is broken the whole of the side that ends with a 

 head is positive to the whole of the side that ends with 

 a tail. 



To the physicist the terminology formerly used by physio- 

 logists was most confusing — in my own case it conveyed 

 an entirely wrong impression until I had made an experi- 

 ment with my own hands. It is most desirable that the 

 anomaly should be removed, and in my opinion it may 

 best be done by dropping the unsuitable terms positive and 

 negative, and saving either that current flows from the 

 more active to the less active part of a tissue or that the 

 one is zincative to the other. George J. Burch. 



University College, Reading, November 11. 



Action of Radium Salts on Gelatin. 



On continuing the experiments detailed in Nature of 

 October -'<>. I found that lead and strontium salts pro- 

 duced the same results upon gelatin as was the case with 

 radium, but the strontium " growths " were much less 

 vigorous than the others. 



On considering the results, it is seen that the metals 

 named are those which form insoluble sulphates, and it 

 occurred to the writer that the " growths " were simpl) 

 a precipitate of some insoluble body formed by the action 

 of the salts used upon the gelatin. 



Various solutions of bouillon and gelatin were pre- 

 pared, and to each were added a few drops of solution 

 of radium or barium 01- lead s.ilts, with the result that 

 in each case a precipitate 11.1- obtained which on careful 

 examination was found to consist of a sulphate, or at 

 all events an insoluble compound, containing sulphur. 



The precipitate produced by the radium s.ili was tested 

 to see whether it was in any way different from that pro- 

 duced bv the barium salt, but. with the exception that 

 it was radio-active, it appeared to be similar in all respects. 

 It was insoluble in strong acids, and gave a sulphide en 

 fusion with sodium carbonate on charcoal, and qualitatively 

 contained no other metal than barium. 



In making the experiments, a few drops of the gelatin 

 were placed on a glass slide, and particles of radium and 

 barium salts added as described in the last communication. 

 The " growths " appeared. Some solution of barium 

 nitrate or radium suit wis now added to the liquefied jelly. 

 The usual precipitate appeared, and this was filtered off 

 through a porous tube. The clear jelly was now tested 

 with radium and other salts, and no growth could be seen 

 even after seven days. 



I think this proves very conclusively what the alleged 

 " growths " are, viz. tl-.at they are nothing more than 

 finely divided precipitates of insoluble barium salts. I 

 have examined these precipitates with the highest micro- 

 scopic power at my disposal, and cannot, in any case, 

 perceive that there is anything of the nature of cell division 

 occurring. 



Of course, many pairs of particles may be found, but 

 the grouping must be purely fortuitous. 



As there is only a limited amount of matter in the 

 gelatin which can be precipitated by the radium, a con- 

 centration occurs at the point of contact of the salt with 



