January 28, 1885.] 



SCIENCE. 



73 



natural waters are concerned, he found the giving-off 

 of hydrogen to he an indication of the presence of 

 microbes, and that the quantity in which the gas is 

 given off appears to increase with the impurity of the 

 water. Thus the waters on the uplands of Derby- 

 shire give off less hydrogen when sugar is added than 

 the same waters taken lower down in the valleys, 

 where sewage enters the brooks. The addition of 

 phosphate to the waters had a powerful stimulating 

 influence ; and as the examination of a soil for phos- 

 phate is a rather tedious process, and the condition 

 of the phosphate a point difficult to examine, Dr. 

 Smith suggests that his hydrogen process may prove 

 useful in the discrimination of rich and poor soils ; 

 also it is a test of the influence of chemical condi- 

 tions on soils and surfaces. And, obviously, if the 

 giving-off of hydrogen is a test of microbe activity, 

 the 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 

 is microbe action suggests the examination of so many 

 substances, that ' the end of the inquiry seems far 

 away.' Having stated his results, and their probable 

 immediate practical utility, Dr. Smith presents specu- 

 lations bearing on ideas which are just now very 

 prominent in the minds of microbiologists. He tells 

 us that he hoped to examine the known microbes of 

 zymotic diseases in order to see if they also produce 

 hydrogen ; and he evidently expected to establish a 

 relation in this way between such microbes and the 

 microbes of upland waters. "It is probable," he 

 continues, " that in sewage we have, at some stage 

 or another, the germs of every disease existing in the 

 community, 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, he inquires, dangerous or otherwise, ac- 

 cording to the conditions to which it is exposed? Is 

 the activity of the microbes found in water diminished 

 by aeration ? Are microbes in water of value, and, 

 as they assist in the production of hydrogen when 

 sugar is present, do they assist in digestion, or are 

 they obstacles to digestion? Do the microbes con- 

 stitute some of the secret qualities of waters which 

 have been found good or evil in 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 the chemical activity of microbes, we have the basis 

 for 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 gives the results of a long 

 series of experiments by means of Dr. Koch's gela- 

 tine process on samples of water obtained from the 



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 is 

 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 shown by both methods. 

 The value of these investigations will easily be seen. 



BARK-LOUSE SECRETION. 



The past summer has been remarkable all through 

 the northern states for the great numbers of large 

 scale or bark lice. These lice have seriously injured 

 our maples, white ashes, hickories, sassaf rases, tulips, 

 and elms. The eggs of these coccids hatch in May 

 and June. 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 suction-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 lice. 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 unctious 

 sweet. 



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 they 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. 

 The 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 in 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 



