April 17, 1879] 



NATURE 



569 



the fibres in the neighbourhood of the section, owing to the 

 extension of the demarcation-current along the ner\'e.^ 



By this electrofonic extension we can explain — or for the most 

 part explain — the so-called "weak currents" of the longitudinal 

 section.- A stimulus applied to the ner^•e near the line of sec- 



FiG. 8. 



tion, according to the law of polarisational increment, should 

 have a greater eflFect than when applied to points more remote, 

 3 nd this experiment shows to be the case. Finally, an excitatory 

 wave travelling along the ner\'e towards the cut end of it must, 

 according to the same law, gradually diminish before it disap- 

 pears entirely in the area of section itself. 



V. Concluding Remarks 



The whole of the electrical phenomena of muscle and nerve, 

 therefore, may be readily deduced from a few very simple pro- 

 positions. Irritable protoplasm responds both to destructive 

 and to exciting influences by an electromotive sign. The 

 altered substance takes on a negative potential with respect to 

 the unaltered. This, together with Ac doctrines of internal 

 transverse polarisation and of the polarisational increment of 

 excitation, appears fully competent to explain all the facts hitherto 

 observed. 



That these fundamental doctrines have the closest reference to 

 the whole life of irritable tissues no one will be disposed to 

 doubt. Yet much examination will be needed to disclose the 

 exact nature of the interdependence. 



Although it must now be confessed that the theories which 

 were based upon facts di-covered more than tliirty years ago, 

 have failed to withstand the criticism of a wider experience, the 

 domain of animal electricity has not lost, but rather gained in 

 interest. And the services of the man who not only discovered 

 this region of phy.-iology, but created the means of conquering 

 it, and who made himself master of its most important funda- 

 mental features, are in no danger of becoming dimmed in our 

 estimation by the theoretical changes we have been compelled to 

 accept. 



BAROMETRIC PRESSURE 

 TN a work of great importance,' recently published by Prof. 

 Bert, on the physiological effects of barometrical pressmre, 

 the author sums up the conclusions to be drawn from his re- 

 searches as follows : — 



A. The diminution of barometric pressure acts on living 

 beings only by diminishing the tension of the oxygen in the air 

 which they breathe, in the blood which animates their tissues 

 (attoxytunne of M, Jourdanet), and by thus exposing them to 

 the dangers of asphyxia. 



B. The increase of barometric pressure acts only by in- 

 creasing the tension of the oxygen in the air and the blood. Up 

 to about three atmospheres this increase of tension gives rise to 

 intra-organic oxidations a little more active. Beyond five 



' " ^'=^1 f- d- ges. Physiol.," vii., p. 363, 1873. This poIarisaticD, of 

 course, ftiU occurs even when the demarcation-current is net abducted, or 

 when the abducted portion is counterbalanced by an opposite current. In the 

 latter case, according to Bosscha's law, the nerve behaves just as if no 

 abducting circuit were applied to it. " Arch, f . d. ges. Physiol. " is p. 20 

 1874 ; X., p. 237, 1873. • ' r y, 



* In Fig. 8 the core of the ner\e-fibre is obliquely shaded. Even in the 

 absence of polarisation of the core the boundary current would become dis- 

 tributed after the manner shown in the figure, and would pass into the 

 galvanometer cu-cu;ts g and g' as the so-called weak longitudinal and trans- 

 verse currents of du Bois-Reymcnd. But, with polarisation, the extension 

 along the core is very much greater than without it, and at the same time the 

 polarisational curve //' is produced. 



' ',',La Pression Barometrique ; Recherches de Phvsiologie Experimen- 

 tale. Par Paul Bert, Professor a la Faculty des' Sciences de Paris. 

 (Pans : G. Masson. 1878.) 



atmospheres the oxidations diminish in intensity, probably change 

 in their nature, and, when the pressure rises sufficiently, are 

 completely arrested. It follows that all living beings, aerial or 

 aquatic, animal or v^etable, complex or mono-cellular — that 

 all the anatomical elements, isolated (blood-globules, &c.) or 

 grouped in tissues, perish more or less rapidly in air sufficiently 

 compressed. This rule appears only to suffer exception for the 

 reproductive corpuscles of some microscopic beings. For the 

 higher animals death is preceded by tonic and clonic con\-ulsions 

 of extreme violence. Among vertebrates the rapid accidents 

 due to the too great tension of oxygen only commence to mani- 

 fest themselves at the moment when the haemoglobin, being 

 saturated with oxygen, that gas enters into the state of simple 

 dissolution in contact with the tissues. 



C. Diastases, poisons, and true virus resist the action of 

 oxygen at high tension. 



D. The inconvenient effects of diminution of pressure may 

 be efficaciously combatted by the respiration of an air sufficiently 

 rich in oxygen to maintain the tension of that gas at its normal 

 value (20*9) . Those of the increase of pressure may be com- 

 batted by employing air sufficiently poor in oxj-gen to arrive at 

 the same result. 



E. Generally the favourable or noxious gases (oxygen, car- 

 bonic acid, &c.) act only on living beings in accordance with 

 the tension which they possess in the surrounding atmosphere, a 

 tension which is measured by multiplying their centesimal pro- 

 portion by the barometric pressure ; the increase of one of the 

 factors may be compensated by the diminution of the other. 



F. When animals possess reservoirs of air either completely 

 closed (swimming bladder of acanthopterygians, &c.) or in 

 communication with the air during decompression alone (swim- 

 ming vessel of the Cyprini, intestines of aerial vertebrates, &c), 

 or in communication with the air during both compression and 

 decompression, but by very small orifices (lungs of aerial ver- 

 tebrates, &c.), the diminution or increase of pressure may have 

 physico-mechanical effects. 



G. Sudden decompression from several atmospheres has only 

 the effect (except for some cases comprised under conclusion F) 

 of allowing to return to the free state the nitrogen which was, 

 under favour of pressure, dissolved in the blood and the tissues. 



H. The beings actually existing in a wild state on the surface 

 of the globe are accommodated to the degree of oxygenated 

 tension under which they live ; all diminution, all increase, 

 appears to be unfavourable to them when they are in a state of 

 health. Therapeutics might make something out of these modi- 

 fications in various patho^ical conditions. 



I. Barometric pressure and the proportion per cent, of oxygen 

 have not always been the same on our globe. The tension of 

 that gas has apparently been, and will without doubt continue 

 to go on, diminishing. There is here a factor which v e have 

 not yet taken into account in biogenetic speculations. The 

 power of reaction against these varioiis modifications leads to 

 the supposition that microscopic beings must have appeared first, 

 and that they will be extinguished by the insufficient tension of 

 oxygen. 



K. It is inaccurate to teach, as is ordinarily done, that vege- 

 tables must have appeared in the earth before animak, in order 

 to purify the air of the great quantity of COg which it contained. 

 In fact, germination, even that of mildew, does not tal e place in 

 air sufficiently charged with CO2 to be fatal to warm-blooded 

 animals. It is quite as inaccurate, as I have observed long ago, 

 to explain the anteriority of reptiles with warm-blooded animals 

 by the impurity of the air tainted with too much CO., ; reptiles, 

 in fact, are more injtu-ed by this gas than birds, and still more so 

 than mammals. 



SCIENTIFIC SERIALS 



The Siizungsberichte of the Vienna Imperial Academy of 

 Sciences (Natural History Section, voL Ixxvi. parts 1-5, and vol. 

 Ixxvii. parts 1-4) contain the following more important papers : — 

 Addenda to our knowledge of annelids, by Dr. Aug. v. Mojsiso- 

 vics. — On the orthoptera of the Senegal River, by Dr. H. Kraus. 

 — On the fauna of the Cypris slates of the Eger tertiary strata, 

 by O. Novak. — On the natmral history of glinmier, by G. 

 Tschermak. — Researches on cystolithes and some similar forma- 

 tions in the vegetable kingdom, by K. Richter. — On the genesis 

 of salt deposits, particularly of those in western North America, 

 by F. Po'sepny. — On the fresh-water fish of South-Eastern 

 Brazil, by Dr. F. Steindachner. — On the "Salse di Sassuolo " 



