176 



SCIENCE-GOSSIP. 



bring periodic famine to our sister island. Apples, 

 pears and all sorts of fruits have their particular 

 microbe enemies. Even flowers are not exempt, 

 witness a recent epidemic that destroyed one 

 season's carnations. At first sight these parasitic 

 visitations might seem doubtful blessings, but they 

 serve an important purpose, namely, that of keep- 

 ing the growth of vegetable life within due and 

 proper limits. It has occasionally happened that 

 British plants or herbs have been transferred to 

 foreign soils and have there spread so rapidly as 

 to supplant the indigenous species and become 

 veritable scourges. In such cases it is probable 

 that the controlling microbe has not been trans- 

 ported with the plant, which is then, as it were, a 

 community freed from the struggle for existence, 

 and spared the beneficent ravages of disease. On 

 such small points as these does the balance of 

 nature depend. 



It was in connec- 

 tion with the diseases 

 of animals that most 

 of our knowledge of 

 germ life was in the 

 early days worked 

 out. There are a 

 large number of dis- 

 eases both in animals 

 and in human beings, 

 the exciting cause of 

 which is now known 

 to be the multipli- 

 cation of microbes 

 within the system. 

 Every year sees 

 additions to this 

 list, and our enter- 

 prising American 

 cousins have al- 

 ready laid claim 

 to the discovery of 

 such species as the 



" germ of madness," and the " germ of death." A 

 striking instance of microbial disease amongst 

 lowly forms is the epidemic known as pebrin, which 

 plays such havoc amongst silkworms, and which at 

 one time threatened to extinguish the silk trade of 

 the South of France. The cause of this disorder 

 was first shown by Pasteur to be a minute germ 

 which invades the moth and eggs. This having 

 been ascertained the remedy was easy. The moth, 

 directly it has laid its eggs, is now examined, and 

 if the germ be detected both moth and eggs are 

 destroyed, and thus the disease prevented from 

 spreading. 



The science of bacteriology has similarly thrown 

 light upon a score of like* diseases, chicken-cholera, 

 splenic-fever, swine-fever, glanders, consumption, 

 and rinderpest, diseases which sweep across a 



Bee-Louse {BrauUi caeca). 



continent carrying off stock by hundreds of 

 thousands ; all these are the handiwork of creatures 

 infinitely little, but infinitely industrious and 

 persevering. How much of the great work of the 

 world is done by little people. Even disease 

 germs are not without their uses for man. It 

 has been proposed to utilize cultures of certain 

 species for the purpose of destroying vermin, 

 and other pests. In Australia an effort is being 

 made on these lines to cope with the invading 

 hosts of rabbits ; possibly the insect powders, 

 rat poisons, etc., of the future will be of a similar 

 nature. 



We see then that germs though infinitely little 

 are infinitely powerful, and that their action, far 

 from being uniformly prejudicial, is to a great 

 extent essential to man's welfare. Germs are the 

 scavengers and fertilizers of the world ; they 



play a great part in 

 our industrial and 

 domestic economy, 

 and act as a regu- 

 lating force in the 

 animal and vegetable 

 kingdoms. Without 

 their help both the 

 animal and vege- 

 table world would 

 cease to exist, nor 

 would it be possible 

 to keep the world 

 sweet and clean. 

 Their life - history 

 throughout is indeed 

 a striking illustra- 

 tion of the fact that 

 the welfare of the 

 greatest is depen- 

 dent on the services 

 of the very least. 



11, Richmond Hill, 



Clifton, Bristol. 



M 



PARASITIC D1PTERON. 



R. C. J. Watkins, of Painswick, Gloucester- 

 shire, has kindly lent us a series of exquisite 

 micro-photographs from which we have selected 

 one for reproduction. It represents a bee-louse 

 (Braula caeca Nitz, x 20). This small parasite, 

 about one- eighteenth of an inch long, and of a 

 rusty-brown colour, is a member of the pupiparous 

 Diptera, which include the forest-fly (Hippobosea 

 equina), the sheep-ticks [Melophagus ovinus), the 

 stag-ticks (Lipoptena cervi), the swallow-fly (Stenop- 

 tevyx hirundinis), the bat-louse, and other species, 

 winged and wingless. The bee-louse is said to 

 have a preference for the drones. It lives upon 

 the thorax of its host, holding to the hairs by the 

 well-adapted pectinated claws of the tarsi. 



