366 



SCIKNTIFIC NEAAAS. 



[April 20, iS 



careful experiments. Rabbits, on the contrary, are 

 much more susceptible to the disease than poultry. 



" Chicken cholera " is one of the diseases which depend 

 on the introduction of a minute organism into the body 

 and its spread in the blood. The following figures, borrowed 

 from La Nature, show its appearance : — Fig. i is the mi- 

 crobe of chicken cholera, cultivated in meat broth. Fig. 2 

 shows the blood-globules of a pigeon attacked with the 

 disease. The efficacy of this remedy has been proved, 

 not merely in what may be called laboratory experi- 

 ments, but on a practical scale. A field of twenty acres 

 belonging to Mrs. Pommery, of Reims, a proprietor of 

 extensive vineyards, had become infested with rabbits to 

 a serioufe degree, and their destruction was resolved on. 

 Here, also, ferrets had been found useless. Some bundles 

 of hay and lucern, sprinkled with a " cultivation " con- 

 taining the germs of chicken cholera, were laid down in 

 the field on December 23rd, and by the 27 th not a rabbit 

 remained alive. The disease evidently spreads from 

 those which have eaten the infected matter to others. 



M. Megnin proposes to use, instead of chicken cholera, 

 another disease peculiar to rodent animals — tuberculosis 

 of the liver. Fig. 3 shows the microbe of this disease in 

 its different stages of development from a to g. This 

 affection is rather more slow in its action than chicken 

 cholera, but it is no less certain, and it has the advantage 

 of not being communicable to poultry. 



We must admit that, from our present knowledge, we 

 do not see a flaw in either of these procedures, and trust 

 that they may prove successful. 



ACCLIMATISATION.— III. 



( Continued from page 350.^ 

 "\1 rHEN we introduce into any country an alien plant 



' or animal, we have not simply the old flora or the 

 old fauna, plus the new-comer. We have brought into 

 play a disturbing element — a ferment, if I may use the 

 comparison — and we have thus set up a process, very 

 like decomposition, in the animal and vegetable popula- 

 tion of the country. Each new plant that can maintain 

 itself outside our fields and gardens, each new animal 

 that can exist in a feral condition, intensifies the struggle 

 for existence, and leads to the extirpation of more or 

 tewer native species. 



The thoughtless will perhaps say, " Let them fight it 

 out, and let the best win." But the species which suc- 

 ceed in the struggle for^existence are not the best /or us — 

 not the most beautiful or the most useful ; often quite 

 the contrary. It seems probable that, though " natural 

 selection " may up to a certain point have increased the 

 number of organic species, yet, if that point is exceeded, 

 its action is rather destructive. In like manner, if com- 

 petition between man and man were totally removed, 

 mankind might degenerate. But if it reaches such a 

 grade of intensity as it has done in our times, it compels 

 men more and more to confine their attention to what is 

 directly lucrative, overlooking all work which may lead 

 to better things in the future. Thus original, creative 

 minds find themselves at a discount. 



How far-reaching may be the effects of the introduction 

 of a single animal species may be seen at St. Helena and 

 at the Cape of Good Hope. In both these regions 

 goats were turned loose by European settlers. One 

 of the most prominent habits of these animals is to 

 browse down seedling trees and shrubs. In consequence, 

 as goats multiplied, and as the old trees in the woods 



died off, there were no young saplings to take their place. 

 The woods disappeared little by little ; the shrubs and 

 low-growing vegetation which had flourished in their 

 shade perished likewise. The birds and the insects 

 which found shelter and nutriment in the trees could not 

 survive. In this manner the native flora and fauna of 

 St. Helena have been so completely blotted out that their 

 nature is a mere matter of conjecture. 



Still, this is not all. When a country is denuded of 

 woods, the rainfall, instead of being moderate and 

 regular, is reduced to violent deluges, with times of 

 withering drought intervening. The soil, being no longer 

 held together by the roots of trees and bushes and by 

 herbage, is torn away by the violent rains, and washed 

 down into the valleys and river-beds ; whilst the uplands 

 remain barren wastes of shingle and rock, henceforth 

 incapable of cultivation. To this state millions of acres 

 of the finest land in the world have been reduced by 

 acclimatisation ! The men who brought the thistle and 

 rabbit into Australia have done an infinity of harm to the 

 human race. 



This subject derives an additional importance since 

 there is, as we are informed, no distinct law in England 

 against importing and turning loose wolves, bears, 

 jaguars, death-snakes, and the like. 



The introduction of new plants, ornamental and useful, 

 has hitherto been attempted in a manner anything but 

 scientific. At present vegetal species from climates 

 warmer than our own, if brought over, are set in places 

 open to the sun, and sheltered from northerly and 

 easterly winds ; in case of severe frost they are pro- 

 tected by means of matting. Or in other cases they are 

 raised in a cool greenhouse, moved into the open air in 

 summer, and left out for a greater length of time, year 

 by year, as they become stronger. 



But our horticultural authorities do not seem suffi- 

 ciently alive to the fact that among a large number of 

 seedlings some may be superior to the generality in 

 resisting low temperatures. We learn from Mr. Jenner 

 Weir that a great number of begonias which a nursery- 

 man had intended to house for the winter were overtaken 

 by one of the morning frosts which occurred so unseason- 

 ably in the autumn of 1885. All the plants, save one, 

 were cut off. It seems by no means unlikely that, if 

 young plants were propagated from this resistant indi- 

 vidual, some one or more of them might be found still- 

 hardier than the parent, and thus, by a process of selection, 

 we might, in the course of successive generations, arrive 

 at a strain of begonias — and, in like manner, of other 

 greenhouse plants — which should flourish in the open 

 ground. 



By a similar process of selection we might seek to 

 develop fruit-trees which should come into blossom later 

 than the ordinary strains, and thus escape the action of 

 spring frosts. It would, of course, be also needful to aim 

 at the production of varieties which mature their fruit in 

 the shortest time. The essential question here, to be 

 answered by experience only, is whether the power of 

 bearing low temperatures, of blossoming late, and yet 

 ripening fruit early, can be obtained without a sacrifice, 

 greater or less, of the valuable properties of the various 

 fruits. But in so untrustworthy a climate as ours, where 

 a temperature of 24° Fahr. may be experienced as late 

 as May 8th, the development of such strains or varieties 

 should be aimed at if our soil is to yield its cultivatots 

 fair remuneration, and is to be secured from falling back 

 into the barbarous condition of " permanent pasture." 



