228 



SCIENCE. 



ON A METHOD OF ISOLATING THE MAMMA- 

 LIAN HEART. 



By H. Newell Martin (Johns Hopkins University.) 



To obtain a mammalian heart isolated from the rest of 

 the body and keep it alive for a time sufficient to allow 

 the examination of the effect of various conditions upon 

 its activity has long been a physiological desideratum. 

 The frog's heart has for years been the subject of minute 

 study but hitherto the mammalian heart has been a 

 baffling object. It seems to have been forgotten that 

 while the frog's heart is a spongy structure having no 

 arteries of i's own, the mammalian heart is a dense organ 

 dependent for its life on a continuous blood flow in its 

 capillaries ; and all attempts hitherto made, so far as I 

 know, have been efforts to apply to the mammal the 

 methods found successful with the frog, with merely the 

 addition of arrangements adapted to keep up the compara- 

 tively high temperature at which the mammalian heart 

 normally beats. By working in another way I have re- 

 cently succeeded in keeping the mammalian heart alive 

 for more than an hour, and beating with perfect rhythm 

 and normal force; the organ is thus made almost as 

 available for study as the heart of the lrcg. The method 

 adopted is as follows: The animal having been narco- 

 tised and the chest opened, the aorta is tied just beyond 

 its arch ; then the trunk whirh, in the cat, gives origin to 

 the right subclavian and the two common carotids, is lig- 

 atured close to its origin, and a cannula put in the left 

 subclavian ; finally, the inferior and superior vense cava? 

 and the azygos vein, and the root of one lung are tied. 



Artificial respiration is of course started so soon as the 

 thorax is opened, and kept up henceforth. The course 

 of the circulation is thus : — left auricle, left ventricle, 

 commencement of aorta (and along the left subclavian to 

 the cannula which is connected with a manometer), 

 coronary system, right auricle, light ventricle, pulmonary 

 vessels of one lung, and then back to the left auricle ; in 

 other words, the only section of the systemic circulation 

 left is that through the vessels of the heart itself. Since 

 the physiological actions taking place in the lung are 

 among the best known of all occurring in the body, they 

 may be eliminated, and we have practically an isolated 

 and well-working living mammalian heart for study. 

 The nerves going to the heart may be divided if desired, 

 but that is hardly necessary as the want of blocd-flow in 

 the nerve centres of the body incapacitates them after a 

 very short time, and they no longer are capable of exert- 

 ing any influence on the heart. It is possible, however, 

 that changes in the lung vessels may affect the results of 

 experiments made on the heart's work under different 

 conditions {e.g. when defibrinated blood is sent into it 

 from a vein under various pressures, or when drugs are 

 administered to it), and an investigation of the nerves, 

 if any, governing the lung vessels must be undertaken as 

 a preliminary to a further study of the direct action of 

 various conditions on the heart's work. 



EDINBURGH ROYAL SOCIETY. 



There was a very large attendance at the meeting of the 

 Edinburgh Royal Society held recently, to hear Pro- 

 fessor Helmholtz, who was announced to make a com- 

 munication "On Electrolytic Convection." Professor 

 Helmholtz stated to the Society the results of certain later 

 experiments which he had made in working out his theoiy 

 of electrolytic convection — experiments which, he said, had 

 succeeded better than his former ones had done. He had 

 entered upon his experiments on account of certain ob- 

 jections that had been made to Farraday's electrolytic 

 law, in connection with experiments which showed that 

 a very feeble galvanic current could be kept up by mode- 

 rate electro-motive force between platinum plates dipped 

 in a slightly acidulated solution, even if the electro-motive 

 force of the battery was not sufficient to decompose the 

 water. He had found, in his earlier experiments, that the 



only effect of the current was to absorb oxygen given off 

 from the atmosphere and to form a new portion of water, 

 and that the whole electrolytic effect was, not to decompose 

 water and to produce a new quantity of elements — hydro- 

 gen and oxygen — but only that on the surface of one plate 

 of platinum oxygen was collected and taken away from the 

 surface of the other. He had, therefore, called these currents 

 electrolytic convection. It was not really a decomposition, 

 but only a transport of one of the products of electrolytic 

 decomposition from one place to another. In his later ex- 

 periments he had got rid of the atmospheric oxygen, by 

 inclosing the whole electrolytic fluid in a sealed glass ves- 

 sel. As a result, he had found that the smallest electro- 

 motive force, down to the thousandth of a Daniell's cell, 

 produced a strong deflection which went immediately back 

 to zero, that there was no continuous current, and that, if 

 they broke the current, they got a deflection of the same 

 character in the opposite direction to the first and direct 

 one. Sir William Thomson, in speaking on the paper, 

 stated that Professor Hemholtz's theory of electrolytic con- 

 vection formed quite an era in electrolytic chemistry. Sir 

 William himself made a communication "On the average 

 pressure due to impulse of vortex-rings on a solid," follow- 

 ing up inquiries suggested by Helmholtz's voitex theory. 

 Professor Tait stated the result of certain calculations which 

 he had made " On the crushing of glass by pressure," and 

 which had been suggested by his recent inquiry as to error- 

 corrections in the use of the Challenger thermometers. The 

 lesult was that with cylindrical tubes made from ordinary 

 Leith plate-glass, he found the glass gave way under a 

 shear of about i-250th, and that the strength of the tube 

 was greater as the walls were thicker and the internal di- 

 ameter decreased. But, however thick the walls might be, 

 or however small the internal diameter, a pressure of 22 or 

 23 tons on the square inch would inevitably crush the 

 strongest glass. 



NOTES. 



M. Daudignv, electrical engineer in Paris, has sent to the 

 Municipal Council a petition asking for authority to estab- 

 lish on the top of the Colonne de Juillet a large electric 

 lamp fed by a magneto-electric machine of fifty horse-power. 

 This enormous light is to be diffused by a large reflector of 

 special construction. — Nature. 



Signor Manet, we learn from an Italian journal, whitens 

 the albumen of blood by means of the electric light ; which 

 is projected by a system of mirrors and lenses, giving a 

 strongly luminous effect. The time required varies accord- 

 ing as the albumen is more or less separated from the fibrine. 

 In general, 24 hours suffices to give complete decoloration. 



Professor Loomis appears still to be experimenting in 

 aerial telegraphy— telegraphing without wires— and it is 

 now said that he proposes to establish communication, 

 through the current which he claims is always found at a 

 great altitude, between one of the highest peaks of the Alps, 

 in Switzerland, and a similarly situated station on the 

 Rocky Mountains, on this continent. 



It has been found by M. Laurent that any ordinary good 

 silvered glass mirror, plane, concave, or convex, and of any 

 thickness, may be rendered a magical one by means of heat. 

 A simple way'of doing this is to heat a brass tube, and ap- 

 ply the end of it to the silvered face. If the mirror surface 

 is opposite a screen, the section of the tube is reproduced 

 in white ; if the former is turned away from the screen, the 

 image (which is seen only after removing the tube) is dark. 

 A cold tube may be used with a hot mirror, and the experi- 

 ment may be otherwise varied. 



M. Duchemin, the inventor of the compass with a circu- 

 lar magnet, now adopted in the French navy, has recently 

 devised, for correcting compasses, a system of magnetic 

 compensators. In place of the straight magnetic bars gen- 

 erally employed he uses magnets ot an annular form. If 

 we magnetise a steel ring, it may have two poles at opposite 

 extremities of a given diameter and two neutral lines. Such 

 rings — round, oval, or of any other form, and with or with- 

 out interruption of continuity— may be utilised for the 

 correction of a compass, by being placed either on the 

 bridge of the vessel or in the binnacle. — Revue Industrielle. 



