SCIENTIFIC

Otago Witness, Issue 1819, 1 October 1886, Page 35

SCIENTIFIC

If a section of the spinal cord of a rabid dog be inserted into the brain of a rabbit by trephining, the latter animal becomes mad in about 15 days ; and when the virus from this rabbit is transmitted to a second, and from the second to a third, and so on, by the same method of inoculation, the rabies soon become more and more pronounced, and the developing or incubation period becomes shorter and shorter, until at the end of 50inoculations a most severe form of madness results in about seven days. The virus from the last rabbit is of great purity and of invariable strength, so that similar sections of spinal cord may therefore be relied upon to produce exactly similar effects. It has been further shown that the virulence of the pieces of cord slowly and quite regularly disappears when kept in dry air and remains unaltered when preserved in carbonic acid gag. An understanding of these principles makes it possible to have constantly on hand hydrophobia poison varying in strength from harmless mildness to deadliest virulence. It is upon these graduated poisons that Pasteur depends for his remakable method of! protecting the animal system from hydrophobia. Experimenting first with clogs, a little meat broth containing weak virus was injected under the skin the ftr»t day, and was followed daily by injections of increasing virulence — that is, preparations from cord of°shorter exposure to air— until in a few clays the fresh or strongest virus was used, when it was demonstrated that, ■ without r injury to the animals, had become entirely * refractory to rabies from bites — even when inflicted before treatment — or inoculations of any degree. The method was first tried on a human subject in July 1885, when immunity ■was conferrad within 10 days on a boy con; sidered to be in great danger. Since then several hundred hitten persons have been treated, and thus far the only failure to prevent hydrophobia has been in a single,

case where the inoculations were attempted too late. Admiral Mouchez has shown that in the bourse of 10 years fully 15,000,000 stars, might be made to recordfcheir exact position ami true relative brightness in a series of large photographic charts! Nothing done by man sincie astronomy was a science can be compared with such a work as this, which yet might be well accomplished in a decade of year?. But oven this, wonderful as it is, seems less impressive-, than what has been done, and what astronomers are even now planning to do, in applying the photographic eye of science to analysing the structure of remote suns. Already tliej' have made the waves of light front many of the leading stars record their story on the tiny shore of photographic film, after journeying millions of millions of miles through space. But now a complete survey ia to be made in this way. A giant eye so constructed tha 1 - not only will it gather, but it will sift, the light from multitudes of stars at once, will be directed iv Rucoession towards different parts of the heavens. >"or an hour at each view will this monstrous eye gaze analysing ly on many hundreds of stars at, once, leaving on record at the close of its survey the photographic spectra of v all those stars, by which the elements present in them, nay the very condition in which these elements exist will be written down in letters and words which (for the astronomer) there is no mistaking. Truly a wonderful era of astronomical research is now beginning. Probably the next half century will reveal more about the millions of millions of tenants of interstellar space than all the years which have elapsed since Hipparchus, noticing a new star, was led to form the first of all known star-catalogues. Hundreds of existing railway bridges which (says a ■ writer in Power and Transmission) carry 20 trairis a day with perfect safety would break down quickly under 20 trains an hour. This fact was forced on my attention nearly 20 years ago by the fractnre of a number of iron girders pf ordinary strength under a five-minute train service. Similarly, when in New York last year, I noticed, in the ease of some hundred of girders in the elevated railway, £hat the alternate thrust and pull on the central diagonals from trains passing every two or three minutes had developed weaknesses which necessitated the bars being replaced by stronger ones after very short service. Somewhat the same thing had to be done recently with a bridge over the river Trent, but the train service being small, the life of tho bars was measured by years instead of months. If ships were always among great waves, the number going to the bottom would be largely increased. It appears natural enougn to everyone that a piece even of the toughest wire should be quickly broken if bent backward and forward to a sharp angle ; but perhaps only to locomotive and marine engineers does it appear equally natural that the same result would follow in time if the bending were so small as to be quite 'imperceptible to the eye. A locomotive crank axle oends but 1-S4 inch, and a straight driving axle a still smaller amount, under the heaviest bending stresses to which they are subject, and yet their life is limited. During the year 1883 one iron axle in 50 broke in running, and one in 15 •was renewed in consequence of defects. Taking iron and steel axles together, the number then in use on the railways of the United Kingdom was 14,848, and of those 911 required renewal during the year. Similarly, during the past three years, no less than 228 ocean steamers' were disabled by broken shafts, the average safe life of which is said to be about three or four years. Experience has proven that a very moderate stress, alternating from tension to compression, if repeated about 100,000,000 times, will cause fracture as surely as a bending to rm angle repeated only 10 times. One of the most interesting lectures delivered last year at the Royal Institution was that of Professor Moseley on seashore life. He pictured the coast region as the most favourable to life of all sorts. In it the ancestors of all the chief living groups of animals originated ; from it spring all the great branches of the genealogical tree of the animal kingdom. . At first sight it might appear that the contjnual dash oE the wave? ftnd scouring of the tide would render the coast region decidedlyinhospitable ; but it is whon dashed into waves that water absorbs most oxygen and therefore contains greater possibilities of a high vitality. Here at intervals as 'this struggle grew too fierce colonies had to branch off' into the dry land and Jnto the deep sea ; for most of the forms possessing the land and the sea to-day can be traced to seashore ancestors. Proofs are not wanting that the vertebrates, with man attheiv head, originated from some inveitebrate very like the Oscidians or Tunicates that abound to-day in shallow waters. Professor Tyndall explains the philosophy pf vaccination as follows : — When a tree or a bundle of wheat or barley straw is burned, a certain amount of mineral water remains in the ashes— extremely small in comparison with the bulk of the tree or the straw, but absolutely essential to its growth. In a soil lacking, or extremely exhausted of, these necessary constituents, the tree cannot live, the crop cannot grow. Now, contagia are Jiving things, which demand Gertain elements of life, just as inexorable as trees or wheat pr barley ; and it is not difficult to see that a crop of a given parasite niay so far use up g, constituent existing in small quantities in

the body, but essential to the growth ol the parasite, as to render the body unfit for the production of a second crop. The soil is exhausted, and until, the lost constituent is restored tho body in protected from any further attack from the sarm; dis.ord«r. Bucsh an explanation of nonrecurrent diseases naturally presents itself to a thorough believer in the germ theory; and such waV the solution which, in reply to a question, 1 ventured to oir'er nearly IT> years ago to an eminent phyaican. To exhaust a soil, however, a parasite less vigorous and destructive than the really -virulent one may suffice ; and if, after having by means of a feebler orgamsm exhausted (ho soil without fatal result*, the most virulent parasite be introduced into the system.it will prove powerless. This, in the language of the germ theory, is the whole secret of vaccination.