588 



NA TURE 



[October 13, 1904 



of a hundred cells, and whether the units were in con- 

 tinuity with one another or only in contiguity. 



A second point which seemed certain was that the proper- 

 ties of the central nervous system required for their explan- 

 ation some structure not present in the peripheral nerves. 

 This structure might be, in part, the nerve-endings of the 

 trophic units, but, in part, it must be referred to the nerve- 

 cells, which, in fact, consisted of different protoplasm from 

 that of either nerve fibres or nerve-endings. 



If the fibrillar theory were true, there were facts which 

 showed that the fibrils must be different in different parts 

 of their course. This was illustrated by the action of 

 nicotine and of other poisons on the different parts of the 

 nervous system. With this modification, the fibrillar theory 

 simply transferred to a part of the cell functions which were 

 commonly supposed to belong to the whole. But it could 

 not be regarded as certain that there were any fibrils at all 

 in the nerve cell, for the microscopic appearances varied 

 considerably according to the method of preparation. 



A point which was much contested was the question 

 whether the trophic units were continuous with one another 

 or not. This point was not of great physiological import- 

 ance, but the physiological facts were best explained on the 

 assumption that the units were contiguous but not 

 continuous. 



The last point considered was whether the unit consisted 

 of a single cell or of many cells. The study of the develop- 

 ment of nerves had led different observers to entirely 

 opposite conclusions. Experimentally, the question was of 

 interest in connection with the regeneration of nerves. 

 Numerous surgeons had found new nerve fibres in the peri- 

 pheral ends of cut nerves, but their observations failed to 

 show that some central connection had not been established. 

 In some recent experiments made by Prof. Langley in con- 

 junction with Dr. Anderson, it was found that without a 

 single exception, the new fibres had become connected with 

 the central nervous system. The balance of evidence was 

 then against the occurrence of autogenic regeneration and 

 in favour of the unit consisting of a single cell. 



Dr. A. Hill stated that he was entirely prepared to give 

 his approval to the neurone theory as defined by Prof. 

 Langley, but he objected that this was merely a statement 

 of the cell theory and did not require the special title given 

 to it by Waldeyer. He was inclined to think that the more 

 light we gained on this subject the more should we find 

 that Bethe's view was correct. Apathy has shown a net- 

 work of neuro-fibrillae in nerve cells of invertebrates. This 

 network is easily shown, and is beyond all doubt a structure 

 existing during life. In the spinal ganglion cells of verte- 

 brates a somewhat similar appearance is obtainable. It was 

 easy to make preparations of vertebrate nerve cells in which 

 fibrillfe were indisputably present, but how far this appear- 

 ance was due to reagents it was impossible to say ; but 

 there was a strong probability that the net arranged itself 

 about an existing system of fibrils. The connecting link 

 appeared to him to be the " thorns," and it was a remark- 

 able fact that the spacing of the thorns corresponded to the 

 spacing of the pericellular network. Far as we were from 

 being in a position to form a conclusion on this subject, it 

 was not impossible that neuro-fibrilla;, Golgi's net, and 

 thorns form a system of conducting fibrils of extreme tenuity 

 and almost infinite complexity. 



Prof. Graham Kerr gave an account of the results of his 

 researches on the development of the nerves in Lepidosiren. 

 His first studies on the mode of growth of the nerves in 

 these animals seemed all in favour of His's view that the 

 nerves developed as outgrowths from the spinal system, but 

 more extended observations upon embryos in various stages 

 of development led him to the conclusion that the fibres 

 originated as strands of undifferentiated protoplasm extend- 

 ing between the neuroblasts of the spinal cord on the one 

 hand and the developing myotonic cells on the other. At 

 a somewhat later stage fibrillae appeared in these strands, 

 and still later a sheath was formed from mesoblastic tissue 

 which surrounded and enclosed the group of fibrilla;. A 

 more doubtful conclusion which might perhaps be drawn 

 was that the original path was one along which impulses 

 surged to and fro, and that consequent upon this use the 

 fibrillary structure was developed as a more convenient 

 substratum for the maintenance and extension of that 

 function. 



NO. 1824, VOL. 70] 



Dr. Mann pointed out that nerve cells might be 

 theoretically in one of three states, viz. separate units, or 

 continuous with one another, or at one time continuous and 

 at another separate. In all embryos at a certain period the 

 motor cells in the cord form a syncytium with scattered 

 nuclei, an arrangement which later on becomes less and 

 less marked until in most cases the cells form separate 

 units. Cells not derived from a common mother cell are 

 never in continuity. He pointed out that great care was 

 needed in drawing conclusions from any preparations where 

 such electrolytes as corrosive sublimate were used for pur- 

 poses of fixation, inasmuch as all coagulation by electrolytes 

 invariably leads to a very distinct fibrillar appearance, this 

 is much less marked after the use of such non-electrolytes 

 as osmium tetroxide or formaldehyde free from formic acid, 

 .^t present, therefore, we are not in a position to make any 

 assertions as to the existence or non-existence of fibrils in 

 nerve cells or in tissues. 



Dr. VV. B. Hardy also directed attention to the treacherous 

 nature of the evidence of fibres and networks in cells. A 

 fibrillar structure can be produced from a perfectly homo- 

 geneous solution of egg-white by fixing it with the ordinary 

 reagents and staining it in the usual way. Again, if a 

 concentrated viscous solution of egg-white be stretched 

 between two points and then treated with the ordinary 

 fixing reagents, it can be shown that the fibrils produced 

 in it run longitudinally, and are connected by less prominent 

 ones which run transversely. These fibrils must, of course, 

 be purely artificial. 



Dr. H. K. Anderson emphasised the point that though 

 the neurones might be physically continuous, yet on the 

 whole they must be trophically discontinuous. Experiment- 

 ing upon very young animals, he had found that section of 

 a post-ganglionic segment led to degenerative changes in 

 the corresponding preganglionic segment. On the other 

 hand, the converse was not true. As a further point against 

 the view that the fibrillae of a preganglionic segment were 

 continued down into the postganglionic fibres, he pointed 

 out that Langley had shown that the mode of termination 

 of the preganglionic fibres in the sympathetic ganglia was 

 not specific, since an ordinary motor nerve can be made to 

 grow dowm to a sympathetic ganglion, and ■ terminating 

 there in its own specific manner could yet establish physio- 

 logical continuity. 



Dr. E. Overton pointed out that it had been proved that 

 the presence of sodium ions was an essential condition for 

 the physiological activity of both muscular and nervous 

 tissues, and, in the second place, it had been shown that 

 both sodium and calcium ions were essential for the proper 

 action of nervous interconnections, thus tending to prove 

 that some third substance intervened between the two units, 

 i.e. that there was discontinuity. 



Dr. W. MacDougall argued that the fact that motor 

 neurones could not conduct backwards was the best evidence 

 of discontinuity. Upon the same hypothesis depended also 

 the simplest explanation of another typical characteristic 

 of nervous activity — the effect of summation of weak stimuli. 

 Moreover, the " law of nerve habit " was most difiicult to 

 explain except on the assumption that there is some inter- 

 mediate structure between successive nerve elements which 

 offers a resistance to the transmission of impulses, a block, 

 however, which can be overcome by the action of appropriate 

 stimuli. 



Prof. Langlev, in replying on the whole discussion, 

 suggested among other points that the strands of material 

 described by Dr. Kerr in the development of nerve fibres 

 might be simply connecting structures along w'hich the 

 nerve fibrillae, i.e. the true nerve element, grew down from 

 the developing neuroblast. 



Prof. E. A. bchafer demonstrated a method of artificial 

 respiration which is a modification of one first suggested 

 by Dr. B. Howard in i860. In Howard's method the 

 patient in a case of drowning is first turned downwards 

 and the back is pressed on two or three times to force out 

 water from the lungs, after which he is turned face 

 upwards. The operator is then directed to grasp the lower 

 part of the chest and to press gradually forward with all 

 his weight for three seconds, then with a push to jerk him- 

 self back and wait three seconds, repeating this eight to 

 ten times a minute. 



This method is simple, can be performed by one person. 



