SCIENCE NOTES.

Gisborne Times, Volume XXVII, Issue 2461, 27 March 1909, Page 12 (Supplement)

SCIENCE NOTES.

THE CELL THEORY. When, in 1839, Theodor Schwann enunciated the cell theory-—which affirmed that all animals and plants are aggregates of self-contained units called cells—he was able to do so without qualification. Every organism is seen to begin as a single cell, and, with growth, this divides so as to form a many-celled body. But in the course of evolution, tho relation of cell to cell has, we now know, become much modified. In the simple colonial animals, which are merely separate cellß held togctlrer in a jelly-like matrix, each cell retains its independence. But the cells of higher plants have ceased to be anatomically distinct. Their protoplasm its continuous with that of the neighboring cells by means of threads that traverse the cell walls; and in the higher animals the individuality of the cell is in many "cares still further lost—the penalty for specialisation of functions. A tendon, for instance, is a continuous rod of fused cells, that have undergone incomplete division. A difficulty of another kind arises when we try to decide what is the essential part of tho cell. Since there are many free cells (the white corpuscles, for example), it is clear that the cell-wall, so important in plants, is not essential in animals. The nucleus and cell-substance remain. But a red corpuscle has neither nucleus nor cell-substance, and it is difficult to deny that the corpuscle is a cell. Cell-growth, again, should be limited in. amount. When a cell reaches a certain size it divides in. two 01 should do so. But in the case of nerve cells each gives off a process or extension which branches repeatedly, and may run a long way without any cell division. Then, again, what a strange part in the business is played by those cells, that- aro in the body, but, in s sense, not of it. Tho cells represent the brick-work of the structure, but these motile cells do not fit- in anywhere. If they had entered the body from without we should not hesitate to call them parasites of commensal type—intruders who do some work in return for the shelter they receive. But we know that they are really detached cells of the living tissues. The old cell theory has to he rewritten, before it can cover modern knowledge.

BACTERIA AND DIGESTION. The ferments of the digestive juices are not the only agents at work in the alimentary canal. Mouth, stomach, and small and large intestine have each their own'special bacterial flora. In herbivorous animals bacteria break up the cellulose of the food-plante-, In our case, however, most of them are not necessary. Guinea-pigs born and bred in an aseptic chamber thrive well, and when killed no germs are found in their alimentary tracts. Only a single bacillus is, it is said, present in the intestines of an infant brought up at the breast; while the bottle-fed baby harbors a bewildering host. Some of our bacteria do help digestion. There is one in the stomach that changes sugar into lactic acid. But,this only happens in the early stages of digestion if the flow of gastrio juice is free. If it is not, various gaseous products are formed by bacteria, producing the symptoms of “flatulence.” Normally there should be no multiplication of bactetria twenty minutes after a meal. In the large intestine if 'there is more bacterial fermentation the less well the stomach has done its work. With good digestion the intestinal bactetria fall immensely in numbers. Whero they are inconveniently numerous the “sour-milk” tree ment may be tried. In countries w in summer the cows are drive' ° mountain pasture milk is only vOU Si down at intervals, and the asan s mainly use it sour. The present are fatal to the i r / ma flora ' The sOur milk of Bulgr m . deTOlo f. ? bacterium of is now cultivated ioriXP° rt - . 14 life impossible for,A r ’* v t UorO?' a. few months. Ex-, dies out itself 1/ _., . . actly .how it ]/ °® > 8 « tols "° <J “° knows. It to>®. , , fV t there is some' justmeaf 1 fnr t/ Hindu’s faith in the lioal- • 101 • ~.s of the Ganges. The water at Be’' rOS con * a]Lns bacteria that are aopio tigers. Thoy destroy cholera phoid.