140 



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\_fune 5, 1884 



were more dangerous than fairly continuous ones. Dr. Stone 

 thought that with good skin contact (as with salt and water) this 

 E.M.F. would be dangerous. Mr. Lecky instanced the reported 

 death of a horse at Bushmills by a shock. — A new speed indi- 

 cator, especially for marine engines, was exhibited by Mr. W. 

 T. Goolden and Sir A. Campbell of Blyfhswood. Its action 

 depended on the rolling of a disk on a cone, the disk traversing 

 a screw driven by the engine-shaft. The disk forms the nut of 

 the screw, and rotates in an opposite direction to the latter. Its 

 position on the screw depends on the surface velocity of the cone, 

 which is kept turning at a uniform rate by clockwork. In tra- 

 velling, the disk makes a series of electric currents which indi- 

 cate its position on a set of dials detached. Recording apparatus 

 can be added. The apparatus was made by Mr. A. Hilger. — 

 Mr. W. Baily exhibited a similar device, in which the cone was 

 replaced by a circular plane or disk. He had invented this 

 independently, and it had the advantage of giving a zero position 

 to the rolling disk, though the cone was the more compact 

 arrangement. The idea of using a screw in this manner was 

 suggested by Mr. Shaw of Bristol some three years ago. 



Berlin 

 Physiological Society, May 2. — Dr. Bender gave a short 

 description of a preparation which he exhibited at the end of the 

 meeting. It was an axolotl in the stage of development in 

 which the heart consists of a tube with a sacular expansion at 

 one part, corresponding to the atrium, and then forms a loop, 

 the ventricle, afterwards passing over into a second expansion, the 

 bulb ; the animal is in this stage still transparent enough to 

 permit of the movement of the blood through the three chambers 

 of the heart being seen distinctly. — Dr. Herter described the 

 experiments which Dr. Lukjanow had made in his laboratory 

 upon the influence of increased tension upon the absorp- 

 tion of oxygen. The question is of physiological import- 

 ance because, if it is decided by experiment in the negative, 

 the existence of an optimum amount of oxygen in the air will lie 

 proved, which would coincide with normal percentage propor- 

 tion of oxygen in the air, whereas if the experiment should result 

 in proving that the absorption of oxygen increases with the in- 

 crease of the oxygen tension, then this oxygen absorption and 

 the consequent oxidations would have to be included in the 

 general combustion processes whose intensity is known to 

 increase with the increased tension of oxygen. The experiments 

 were conducted after the method of Regnault and Reiset. The 

 animals were placed inside a bell-jar, into which the air entered 

 on one side along with an additional quantity of oxygen, which 

 could be varied at pleasure, and from which it was drawn off on 

 the opposite side by a tube which passed into the absorption 

 vessels where the carbonic acid was removed, and the residue 

 was provided with fresh oxygen and led back into the bell-jar. 

 An offset from the air tube allowed of a sample of the expired 

 air being drawn off at any time for analysis. In all fifty animals 

 were experimented upon, which were kept fasting for half a day 

 before commencing the experiment. The oxygen of the inspired 

 air varied between 30 and 90 per cent. The mean result of all 

 the experiments on guinea-pigs, rats, dogs, and cats, was a slight 

 increase of the oxygen absorption, to wit 104 volumes as against 

 100 absorbed from normal air. Dr. Herter is of opinion that 

 this small increase cannot be regarded as a consequence of the 

 increased oxygen tension, because, in individual animals, the 

 means of oxygen absorption sometimes fell below, and sometimes 

 exceeded the normal amounts, and further, because they did not 

 vary proportionally with the increased tension of oxygen in the air. 

 The small increase of the general mean must be referred to other 

 causes, i.e. the movements of the animals during the experiments. 

 No increase of temperature was observed under the increased 

 pressure of oxygen. Further experiments were made upon ani- 

 mals in which one could assume an increased demand for oxygen 

 in consequence of high fever being present, but not even 'lid [he 

 animals that had fever take up more oxygen from the air that 

 was charged with a more than normal amount of oxygen. Like- 

 wise, animals from whom a large quantity of blood had been 

 withdrawn behaved in exactly the same way as normal animals 

 in presence of the surplus of oxygen. The conclusion to be 

 drawn from all these experiments is that the absorption of oxygen 

 is not an ordinary combustion process, and that the normal com- 

 position of the atmosphere contains an optimum percentage 

 amount of oxygen. — Prof. Busch spoke about caries of the teeth 

 which has been so little scientifically investigated, because in 

 studying it the external hurtful processes have been alone con- 

 sidered, whereas the second important factor, the resisting power 



of the teeth, has been quite overlooked. In regard to the latter, 

 Prof. Busch called attention to the fact that caries of the teeth 

 had been observed in no animal, and that it appeared to be 

 peculiar to man. Caries of the teeth, however, appears not to 

 be a characteristic of civilised man alone, but it has been ob- 

 served in large collections of skulls even in those of prehistoric 

 time. Some races are more disposed to it than others. For 

 instance, the Celtic, Arabian, and Polish races appear to possess 

 a relative immunity. This is less the case with the Indo-Ger- 

 manic race. Certain families are particularly predisposed to it. 

 General habit of body has a pronounced influence upon its 

 development, as well as menstruation and pregnancy in women, 

 chlorosis, typhoid, &c. Disposition to caries shows itself even 

 in the developing tooth in the composition of its enamel, which 

 is undulating, whereas teeth with quite smooth enamel have 

 much greater power of resistance. The enamel appears to 

 be the only tissue in the body which is subject to no 

 metabolism, and which remains quite unchanged. Every 

 alteration in it which is caused by external influences, and every 

 defect of the enamel remains during the whole of life, and can 

 never be repaired. Dentine also shows differences in its struc- 

 ture as regards its disposition to caries. The dentine tubes either 

 run regularly close side by side to each other, such teeth having 

 a greater power of resistance ; or the dentine tubes branch and 

 surround cellular bodies, or even small air vesicles, such teeth 

 falling an easy prey to caries. If dentine has been decalcified at 

 any place by the action of acids, it undergoes putrefaction under 

 the influence of bacteria which do not seem to belong to any 

 specific species. Dentine is sensitive, although nerve filaments 

 have not as yet been traced into it. Actual toothache does not 

 occur in the course of caries until it has reached the pulp. The 

 inflammation of the pulp is particularly violent and painful, be- 

 cause the tissue is so richly supplied with blood-vessels and 

 nerve-filaments. As the products of inflammation cannot escape, 

 they collect and work their way downwards, where they produce 

 the most painful inflammation of the roots and the periosteum. 

 The chief object of the rational treatment of caries of the teeth 

 consists in the removal of every particle of carious substance out ot 

 the diseased tooth and to protect the sound dentine that has been 

 exposed against external injurious influences by covering it with 

 a firm substance which is not attacked by acids : gutta-percha, 

 cement, or gold. Although the dentine is not as unchangeable as 

 the enamel, but manifests, by its becoming firmer or softer, that 

 it is not quite uninfluenced by tissue changes, yet its caries is 

 not an irritative process that the dentine takes an active part in, 

 but a passive process, and consequently the removal of all 

 diseased portions, and the protection of the non-carious part of 

 the tooth by filling with a resistant mass suffices to stay the 

 morbid process completely. 



CONTENTS page 



The Origin of the Crystalline Schists. By Arch. 



Geikie, F.R.S 121 



Letters to the Editor :— 



The Marine Biological Association. — Prof. E. Ray 



Lankester, F.R.S 123 



The Equatorial Coude of the Paris Observatory. — 



Howard Grubb, F.R.S 123 



The Earthquake.— J. Henry Kinahan ; W. F. 



Stanley ; Rev. O. Fisher 124 



Jupiter. — W. F. Denning 125 



Animal Intelligence. — Col. J. Herschel ; Antoine 



d'Abbadie 125 



Meteorology in Victoria 126 



Habits of Burro wing Crayfishes in the United States. 



By Ralph S. Tarr. (Illustrated) 127 



The Young Gorilla of the Jardin des Plantes. 



(Illustrated) 128 



Notes 129 



Our Astronomical Column :— 



The Total Solar Eclipse of 1SS9, January I . . . . 131 



Variable Stars ■ 131 



Geographical Notes 131 



On the Nomenclature, Origin, and Distribution of 

 Deep-Sea Deposits, III. By John Murray and Rev. 



A. Renard 132 



The Fixed Stars. By David Gill, LL.D., F.R.S. 



(Illustrated) 135 



University and Educational Intelligence 137 



Societies and Academies 137 



