PROCEEDINGS OF THE SOCIETY OF ARTS

FOR THE TWENTY-EIGHTH YEAR.

MEETING 392.

Biological Water Analysis.*

BY PROF. W. T. SEDGWICK.

The 392nd meeting of the SOCIETY OF ARTS was held at the Institute on Thursday, October 10, 1889, at 8 P.M., Hon. J. A. Dresser in the chair.

After the reading of the records of the previous meeting, the Chairman introduced Prof. W. T. Sedgwick, of the Institute, who read a paper on "Biological Water Analysis."

Prof. SEDGWICK said: A biological analysis of water, strictly speaking, is an impossibility. Water may be analyzed chemically and resolved into its components, hydrogen and oxygen, but a biological analysis of water is an impossibility, because water is absolutely lifeless and inorganic. By a chemical" water analysis," however, the chemist does not usually mean the analysis of a portion of pure water, but only a chemical examination of the substances dissolved in, or carried by, the water. In precisely the same way a biological "water analysis" is understood to be simply an examination of the organisms present in a particular portion of water.

The biological analysis of a water must deal with all the organisms which can be detected therein; but inasmuch as the coarser water-dwellers the fishes, the frogs, the snails, the water-weed, etc. are seldom collected in a sample for water analysis, there are usually present only the very small, and often quite invisible, organ

* Revised from an address published in the Journal N. E. Water Works Association, September, 1889,

isms which may nevertheless be exceedingly numerous. Practically, therefore, the biological examination is directed to the inconspicuous forms of life, which often swarm in waters, even in those used for drinking. Taken as a whole, these organisms are known as the "microorganisms," and form a vast group of living things, some of them nearly, and some of them quite, beyond the vision of the naked eye. In dealing with the microorganisms in a sample of water, or in a water supply, the coarser organisms must by no means be neglected; but the biological analysis of water as at present conducted is concerned especially with the microorganisms; and in the present paper no great departure will be made from the prevailing point of view.

Microorganisms are of two different kinds, and must be studied in two very different ways. Although all might perhaps be described as "microscopic" in size, those in one group are so much smaller than those in the other as to be almost smaller than "microscopic." These smallest microorganisms are the bacteria; and, although they may be seen by the help of the microscope, and, indeed, can be seen individually in no other way, they cannot be satisfactorily studied still less counted by the microscope alone. These organisms-the bacterial - are therefore detected and chiefly studied by the method of "cultures," otherwise known as "Koch's method," which I have already had the honor to describe and demonstrate at a meeting of this Society some two years ago. Of the bacterial microorganisms I shall speak tonight only incidentally, although within that time our knowledge of them and of their doings has been steadily advancing.

On this occasion I desire rather to turn your attention to the second division of the microorganisms, the microscopical. This includes all microorganisms except the bacterial, and is separated from that group by the fact that while the latter require for their satisfactory study the employment of "cultures," the microscopical microörganisms may be detected, counted, and pretty fully studied by the microscope alone.

In a summary fashion the relations of these groups may be shown as follows:

MICROORGANISMS.

Organisms, either plants or animals, too small to be studied with the naked eye.

MICROSCOPICAL ORGANISMS.

Not requiring special "cultures." Easily studied with the microscope. Microscopic in size, or barely visible to the naked eye. Plants or animals.

BACTERIAL ORGANISMS.

Requiring special cultures for their satisfactory study. Difficult of study with the

microscope, because almost sub-microscopic in size. Plants.

The bacterial microorganisms include the bacteria, as well as some yeasts and moulds. The microscopical microorganisms include a great variety of animals, such as minute entomostraca, like Cyclops and the water flea; various worms and wheel-animalcules; sponges and the fresh-water Hydra; infusoria, rhizopods, and such like; and among the plants, the diatoms, algæ, fungi (excepting those already mentioned), and the so-called "blue-green algae." Beside the bacteria these forms are mostly of giant size, and hence may be seen and studied with comparative ease by the aid of the microscope alone.

I am the more anxious to urge upon your attention the microscopical microorganisms since it is with them that some of the more recent progress has been made in the biological analysis of water. Furthermore, it is in this field, in all probability, that some of the most interesting developments of the next year or two will be found. These are the organisms that often pave the way for the bacteria in water, and possibly therefore for the germs of disease. These are the organisms which are, in large measure, the source in water of the "organic nitrogen" (or albuminoid ammonia) of the chemists; the organisms, responsible in large measure, for odors, tastes, and turbidities in waters, either directly by their own activity, or indirectly by amassing organic matter, and eventually surrendering it as putrescible food for the more destructive bacterial organisms.

As long ago as 1850 Dr. Arthur Hill Hassall made a microscopical examination of the water supply of London, perhaps the first ever scientifically made anywhere, and, in discussing his results, wrote afterwards as follows: "The deleterious properties of impure water depend, for the most part, on their organic impurities.

*

*"Food and its Adulterations," p. 55, London, 1885.