Feb. 25, 1 886] 



NA TURE 



395 



A better chance of seeing them could hardly be. They 

 were at all times to be away from the sun's light, and 

 when nearest to the earth not more than one-fifth the sun's 

 distance. The paths were carefully computed, and the 

 action of all the planets, notably that of Jupiter, allowed 

 for. A dozen observers for months swept the heavens 

 with their telescopes, but not the slightest trace of the 

 comets was seen. 



.•\gain, they should have come to perihelion a year ago 

 last autumn (Oct. 6, 1S72), but, as I suppose, neither of 

 them was seen. With the loss of its hero, our story would 

 seem to come to an end. I must ask your indulgence, 

 however, for another chapter. 



I suppose that each one of you has often seen a shoot- 

 ing-star. On a clear night you have seen a bright point 

 of light travel quickly across the sky, as though a star 

 had been shot from its place in the firmament. It may, 

 if it was a large one, have broken into sparks as it dis- 

 appeared, or have left a cloudy train along part of its path 

 for an instant ; or perhaps it was so faint even that you 

 could not be quite sure that you saw anything. Some of 

 you have seen those shooting-stars by hundreds in star 

 showers. 



Until near the close of the last century, poets dreamed, 

 and other men guessed, about these objects, but knew 

 nothing. Two German students, Brandesand Benzenberg, 

 found out, and told us, that these bright flights were in 

 the upper parts of the atmosphere. From the two ends 

 of the city a track always appeared to be in the same part 

 of the heavens. But when one went to a village many 

 miles away, a track was seen by the two persons (at ."Vand 

 B, Fig. 8), in different parts of the sky. Hence they 

 ■were able to measure the height of the shooting-stars 

 from the ground. 



We now know that these luminous paths are rarely less 

 than 40 miles or more than 90 miles from the earth. We 

 also know that any shooting-star was a small body, of 

 unknown size, perhaps not larger than a pebble or a grain 

 of coarse sand even, undoubtedly solid, which has been 

 travelling around the sun in its own independent orbit, 

 like any planet or comet. Its path came within 4000 

 miles of the earth's centre, and so the small body struck 

 into the earth's atmosphere. Its velocity was so great — 

 fifty or a hundred times that of a cannon-ball— that even 

 in our rare upper atmosphere an intense light and heat 

 was developed by the resistance, and the body w-as 

 scattered in powder or smoke. These bodies before they 

 come into the air, I call meteoroids. It is only when they 

 have reached our atmosphere and begin to burn that we 

 ever see them. They are then within 90 miles of the 

 ground. 



[To be cpi!ti?!iicd.) 



ON THE COAGULATION OF BLOOD ^ 

 OROCKE'S researches on the conditions of coagulation 

 ■'-' of blood have shown that, on the one hand, contact 

 with foreign bodies makes blood coagulate, and, on the 

 other, that contact on all sides with the fresh vascular 

 wall obviates coagulation (Durante). Lacker has proved 

 the influence of foreign bodies on blood-coagulation by 

 microscopic observation of coagulation in its first stages. 

 In partial contradiction to these results was the observa- 

 tion'of Griinhagen that blood, when received into glycerine, 

 and so long as it did not mix, remained liquid. To deter- 

 mine the nature of these influences the following e.\peri- 

 ments were made. Blood was drawn under oil from the 

 carotid artery of a dog, and let stand at ordinary indoor- 

 temperature ; after twenty-four hours it was not coagu- 

 lated. Then the blood was drawn into a vessel smeared 

 inside with vaseline, and it too tfid not coagulate. When 

 it was stirred with an oiled glass rod, no fibrin was 

 separated ; but when, even after several hours, part of 



' By Ernst f'reund, in Wiener mcdkinh.hc Jahrlmchir, iSS5. Heft i. 



this blood was poured into an ungreased vessel, it coagu- 

 lated in a few minutes. Moreover, contact with an un- 

 greased glass rod sufficed to make the blood in the 

 greased vessel coagulate outwards from the rod. 



Further e.xperimeaits showed that the drying of the 

 upper layers of the blood, and the presence of small 

 quantities of dust, caused coagulation even in the 

 greased vessel ; if this was guarded against, the blood 

 remained liquid for days, and the corpuscles sank to the 

 bottom, the plasma remaining as a clear liquid above. 



After pouring out the blood, the greased walls of the 

 glass vessel showed neither blood-colouring matters, nor 

 traces of a separated albuminous body. A repetition of 

 these experiments at 37^ C. gave the same result. In all 

 the experiments blood was also, for comparison, drawn off 

 into ungreased vessels, and in all these it coagulated, at 

 the most, in a quarter of an hour. 



In further experiments a small vaseline-lined glass tube 

 was used as a canula ; and the blood drawn through this 

 into vaseline-lined vessels also remained uncoagulated. 



When the outer orifice of a canula inserted in the 

 carotid was closed, the blood column in it pulsated, without 

 showing the least sign of coagulation even after two hours. 



In all these experiments there was nowhere in the 

 vessels with which the blood came into contact even a 

 point for adhesion — such a point would have caused in 

 shorter or longer time coagulation of the whole mass of 

 blood. Thus the coagulative influence of foreign bodies 

 appears to be due to their adhesion. 



But to demonstrate that the anti-coagulative property 

 of the vascular walls is due to the lack of adhesion, a 

 further series of experiments was made with soaked fish- 

 bladders and parchment-tubes. 



The membranes lay several hours in o'6 per cent, 

 chloride of sodiunr solution ; the blood was drawn off 

 through a vaseline-lined canula into the bladders and 

 tubes, which were then so hung in a litre of the salt- 

 solution that the mass of blood was under the surface. 

 In these experiments also the blood remained liquid, 

 the surrounding salt-solution having no coagulative effect, 

 while some of the blood, poured after twenty-four hours 

 into an ungreased porcelain \-essel for comparison, soon 

 coagulated. Like the blood-vessels, which, unlike manu- 

 factured vessels, after being emptied of the blood, retain 

 no colouring-matter, the membranes, even after several 

 days, showed neither imbibition with blood-colouring 

 matter, nor any trace of coagulated fibrine. Thus, by 

 soaking in salt-solution, a property of the blood-vessels 

 was imparted to the fish-bladders and parchment-tubes. 



It can hardly be doubted, then, that while, on the one 

 hand, lack of adhesion prevents blood from coagulating, 

 so, on the other, the presence of adhesion gives the 

 impulse to coagulation. 



INOCULATION AS A PRESERVATIVE 

 AGAINST CONSUMPTION 



MVERNEUIL has lately pubHshed a letter to the 

 • editor of the Gazette hcbdominaire, M. Lereboullet, 

 in which he proposes to set on foot an experimental 

 inquiry into the possibility of finding some method of 

 "attenuating" the presumed virus of tubercle, so as to 

 make inoculation therewith practically useful against 

 consumption, either as a prophylactic measure, like vac- 

 cination against small-pox, or as a means of cure, like 

 Pasteur's inoculations in hydrophobia. 



Three thousand francs have already been subscribed, 

 and the respectable names of Cornil, Bouchard, Dama- 

 schino, and Potain are mentioned among those who 

 approve of the investigation. 



It must however be remembered (i) that with the 

 exception of hydrophobia, an exception still on trial, no 

 human disease but small-pox is known which can be 

 prevented by inoculation ; (2) that of epizootic diseases 



