224 



SCIENTIFIC NE^VS. 



[Dec. 1st, 1 5 



A WORD FOR "GERMS." 



WE have heard of late so many alarming things con- 

 cerning the activity of germs, microbes, or micro- 

 organisms in the propagation of disease, that many of us 

 look upon these tiny beings as unmixed evils, and wish 

 that they could be entirely swept away from the earth. To 

 do so, had we the power, would be a mistake, the conse- 

 quences of which would not be slow in making their ap- 

 pearance. We must remember that there are germs and 

 germs. Some of them, commonly known as morbific 

 germs, are supposed to be at least the ultimate causes of 

 disease^, the more immediate or proximate causes being 

 certain poisonous compounds which these morbific germs 

 generate if they succeed in penetrating into the living 

 animal body. 



But there are other " germs " which are not concerned 

 in the propagation of pestilence, but whose function is to 

 effect chemical changes in dead matter. 



Perhaps the best known instance of the activity of such 

 germs is the process of fermentation by which the decoc- 

 tion ot barley is converted into beer, and the juice of the grape 

 into wine. But we must well note that the agents even in 

 these two cases are not strictly identical. Beer-yeast, if 

 added to grape-juice, certainly breaks up the sugary matter 

 present into carbonic acid and alcohol, but the wine thus 

 obtained is inferior. On the other hand, the so-called 

 ellipsoid ferment, which is found naturally adhering to the 

 skins of grapes, if added to a solution of sugar, or to a de- 

 coction of malt, produces a fermented liquor of a decidedly 

 vinous flavour. 



. Here, then, we have a very simple instance how one and 

 the same kind of matter may yield very different products, 

 according to the kind of ferment with which it comes in 

 contact. 



But sugary solutions may yield quite other products, if 

 we introduce into them still other ferments. One of these 

 converts such solutions into vinegar, and is known as the 

 acetic acid ferment. Another kind yields lactic acid — an 

 acid met with in sour milk and in the contents of the 

 stomach in certain kinds of indigestion. Sometimes the 

 brewer finds to his cost that the acetic or lactic acid fer- 

 ments, or both, have invaded his vats and have overcome 

 the beer-ferment. In this case the product is an acid 

 liquor, often utterly unsaleable. He has, therefore, to 

 study the conditions for keeping his ferment pure, and from 

 preventing the introduction, as far as possible, of the acid 

 ferments. 



But we shall be much mistaken if we suppose that the 

 utility of germs is confined to brewing and to the produc- 

 tion of wine and vinegar. If this were all, we might, per- 

 haps, be told by a numerous body of thinkers that their 

 activity was productive of much more harm than good to 

 the human race. They play a great part in agriculture, or 

 rather in certain natural operations upon which the pro- 

 duction of the food of plants depends. We know how that 

 if the remains of dead animals and plants are left to them- 

 selves in an enclosed atmosphere, perfectly sterilised, that 

 is freed from all of these germs, they do not decay, and 

 are in consequence never resolved into manure. But the 

 germs of putrefaction are everywhere in nature, in the air, 

 in the water, and in the soil, and they quickly break up 

 lifeless organic matter into states in which it is fit to serve 

 for the food of plants. Thus the great circulation of life in 

 the world is kept up, the remains of past generations serv- 

 ing as food for their successors, present and future. To 

 arrest this play would be to bring life, or rather the possi- 

 bility of life, to an end. Certain interesting researches, in 

 which Mr. Warington has taken a leading part, show that 



in the upper layers of arable and pasture lands there exists 

 a kind of germ busily engaged in converting the nitrogen 

 of defunct animal matter into nitric acid. This is the 

 rationale of nitre-beds, in which urine, blood, etc., are con- 

 verted into saltpetre, the acid combining of course with 

 alkaline matter present in the soil. In this state the nitro- 

 gen is most readily assimilated by growing plants. 



The question is farther raised whether such germs in the 

 soil do not do a something beyond merely bringing the 

 nitrogen present in the excretions and the remains of ani- 

 mals fit to be used over again. The recent researches of 

 M. Berthelot seem to indicate, if they do not actually de- 

 monstrate, that through the instrumentality of such germs 

 the soil is able to seize upon the free nitrogen of the atmos- 

 phere and convert it into ammonia and nitrates ready for 

 the maintenance of plants. 



Other germs seem to be engaged in the important task of 

 purifying the waters — freeing them from organic pollution. 

 At least Dr. Dupre has been led to this conclusion by his 

 recent observations and experiments. 



If this view is correct we are placed in a curious dilemma, 

 as far as the purification of foul waters is concerned. Some 

 authorities maintain that a process of filtration or precipita- 

 tion, to be successful, should remove all germs from water. 

 If not, disease-germs may be present. But if we were to 

 thus free it entirely from all micro-organisms we should 

 remove the useful micro-organisms along with those which 

 are the bearers of disease. Agents or processes which 

 would destroy the one would destroy the other also. In 

 practice, however — perhaps fortunately — this difficulty can 

 never arise. We cannot free water from germs ; do what 

 we please, a fresh supply will be constantly introduced by 

 the air, the rain, and by dust. 



We may find germs playing yet another part, sometimes 

 useful and sometimes hurtful, in indigo-dyeing. Most 

 persons know that indigo, in its ordinary commercial state 

 is insoluble. If brought in contact with certain chemicals 

 it is dissolved, and at the same time reduced to a pale 

 yellow substance known as white indigo. If textile goods 

 are immersed into it in this state and are then exposed to 

 ■the air, the white indigo which adheres to the fibre is re- 

 converted into ordinary blue indigo by the oxygen of the 

 atmosphere. This change of blue to white indigo is effected 

 where woollen goods are concerned by a process which is as 

 true a process of fermentation as that conducted by the 

 brewer, though a different ferment-germ comes here into 

 action. But again, just as in brewing, false ferments often 

 find their way into the vats, wasting more or less of the 

 indigo, and occasionally destroying it altogether, thus 

 occasioning a heavy loss. Hence great skill and much 

 experience are required on the part of the indigo-blue dyer 

 — though hitherto he has worked by rule of thumb — to 

 guard against such false fermentations. It is now found 

 possible to breed or cultivate the genuine ferment in a state 

 of purity and to add it to the indigo in place of the empirical 

 mixtures of grape-sugar, bran, urine, woad, madder, rhubarb- 

 leaves, etc., which have been used to set up fermentation, 

 and which were exceedingly likely to bring with them 

 germs which were not wanted. 



The process by which indigo is extracted from the indigo 

 plant is also a fermentation in which various germs may 

 take part. Hence it sometimes proves a failure. If the 

 conditions of the process were closely studied it would 

 doubtless be found possible to breed the proper ferment in a 

 state of purity and give it exclusive play in the vats. We 

 think it likely that by attention bestowed in this direction 

 not merely the quantity but also the quality of the indigo 

 harvest might be strikingly improved. 



One concluding reflection may here be permitttd ; we 



