Page:Science vol. 5.djvu/87

 lutanl waters are concerned, be found the giving-oH of hydrogen to be an Indication of the presence of mlcrobei, uid that the quantity in which the gas is gjren off appears to inFrease with the Impurity of the water. Thus the watera on the uplands of Derby- shire give off less hydrogen when sugar ia added than the SAine waters taken lower down in Iha valleys. There Mwage enters Iho- brooks. The addition of pho«pbal« to the waters had a powerful alimulaiing InlluenMi; and as the esamination of a soil for pliOB- pbal« is a rather tedious process, and the condition

I •( the phosphate a point difficult to examine. Dr.

I Bmltli suggests that his hydrogen process may prove nseful in the discrimination of rich and poor soils; also It ia a test of the influence of ciiemicol condi- ^OOB on soiU and surfaces. And, obviously, it the gliing^jff of hydrogen is a lest of microbe activity, lh« process applied to soils may afford a test of the miasmatic condition of particular localities. Indeed, Dr. Smith himself observes that the new light which the process promises to throw upon cases where there i* microbe action suggests the examination of so many rabstances, that * the end of the inquiry seems far ■way.' Having slated his results, and Ibeir probable immediate practical utility, Dr. Smith presents specu- lations bearing on ideas which are just non Ter7 prominent in the minds of microbiologists. He tells us that be hoped to examine the known microbes of xymotlc diseases in order to see It they also produce hydrogen; antl he evidently expected to establish a relation in this way between such microbes and the microbes of upland waters. "It is probable," lie continues, " that in sewage we have, at some stage or another, the germs of every disease existing in the comraonitj, and perhaps, if Intensified enough, the germs of every possible disease;" and later on he states the problem still more definitely. Is any germ of disease, be inquires, dangerous or otherwise, ac- cording to the conditions to which it is exposed? Is theactivity of the microbes fonnd in water diminished by aeration? Are microbes in water of value, and, as tbey assist in the production of hydrogen when sugar is present, do they assl<t in digestion, or are they obstacles to digestion? Do the microbes con- stitute some of the secret qualities of waters which havebeenfoundgoodoreviliu the opinion of so many of mankind? In other words, is absolutely pure water wholesome? A curious speculation in which he indulges is, that, given the hydrogen test as a measure of tbechemicolautivityof microbes, we have the basis (or calculating the electrolytic power of the move- ments involved In the life of a single microbe, and thus for arriving at the mechanical equivalent of a disease-germ. In the second part of his water report, Dr. Smith has described additional experiments on the elimination of nitrogen during putrefaction in water, offering further evidence of what he calls the natural purification of waters (first by putrefaction, and then by oxidation) in continuation of the interest- ing exposition in the report for 1882.

In a third part. Dr. Smith given the results of along series of experiments by means of Dr. Koch's gela-
 * # process on samples of water obtained from the

��^^^^piB process on

��most varied sources. The method consists in mixing a purified solution of gelatine with the water experi- mented upon. In very Impure waters the gelatine Is first rendered fluid at the surface: and this fluidity gradually increases until the whole becomes fluid. The fluid swarms with bacteria. The results are registered by photographing the test-tubes. It ia significant that the results by the gelatine process correspond very fairly with the indications by the hydrogen process, approximate gradations of activity in the same waters being sliown by both methods. The value of these Investigations will easily be seen.

��BARK-LOUSE SECRETION. The past summer lias been remarkable all through the northern states for the great uumbers of lai^ scale or bark lice. These lice have seriously injured our maples, white ashes, hickories, sassafnues, tulips, and elms. The eggs of these coccids hatch In May and Juno. The young lice attach their force-pumps beneath the leaves, where they sap the vigor of the trees the summer through. As the drying-up of the leaves in autumn gives a prophecy of a weakening stem, and prospective fall of the leaves, the lice desert the leaves, and attach their auction-pumps to the under side of the twigs and branches. I found that I could, by plucking the branches, hasten the migration of these lice from leaves to stem. The premature drying of the leaves caused the premature emigration of the iice. In early spring the scales — for now the lice are plump, scale-like creatures — grow very fast; and so rapid is the nectar secretion which exudes from the lice, that the leaves twinkle and fairly drip with this bark-louse nectar. The grass and walks beneath the trees become sticky with the i

��The species of coccid which infests the maples se- cretes a cotton-like, fibrous mass, in which the eggs to the number of seven hundred or eight hundred are placed. This cotton-like nidus pushes out from be- hind, and raises the scale from the branch. In other species the hundreds of white eggs are concealed be- neath the brown scales.

The nectar from these bark-lice is dark in color, of rank odor, and bitter and unpleasantly pungent to the taste. Though the bees appropriate this secretion, they refuse it entirely when tbey can gather from flowers. In actions they say, ' Better this than none, but never this when other Is possible.' The bees re- gard this questionable sweet just as they do grape- sugar,— only to be accepted In lieu of naught else. "Vhe odor of this nectar is so rank, that Its presence on trees Is often quickly detected when one passes by. In many sections the past season the bees gath- ered this liquid by tons. I know of cases where the odor i[i the apiary was so strong that the bee-keepers thought they were victims to that terrible fungoid malady, 'foul brood,' which bee-disease is indicated by a nauseating stench.

This bark-louse nectar presents a strong contrast

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