could, by a simple mechanical contrivance, | tance to which they could be carried, and be removed without disturbing anything to which they could spread contagion, is else. Twenty-four hours after the expos- practically unlimited. The bearing of this ure of the open basins to the mote-laden on the germ theory is obvious enough. atmosphere, the covers of the others were removed, and everything was left for a Some months since, the spontaneous certain time, after which first the open and generation controversy arrived at an imsubsequently the remaining basins were portant crisis. Results of the most conexamined. It was then found that in flicting character had been obtained by those which had been exposed to the air different observers, and a settlement of the from the first the calycine monad occurred question seemed further off than ever. in every drop taken from every vessel, and But, about the middle of last year, Dr. the springing monad in two-thirds of the Bastian earned the gratitude of biologists drops examined. In the vessels which by narrowing the point at issue, and givhad not been exposed until the air had set-ing, for a time at least, a definite direction tled for twenty-four hours, the calycine to future experiments. He announced, at form was wholly absent in three vessels the meeting of the Royal Society on the out of four, and in the others occurred 15th of June,* that he had discovered the only in four drops out of thirty, while the precise conditions under which living orspringing form flourished in every vessel. ganisms were infallibly produced in cerThe reason of these facts is very curi- tain putrescible but sterilized organic ous and very interesting. The calycine fluids. If this supposed discovery were a monad is a giant of its kind, being about real one, its importance could hardly be one nine-hundredth of an inch in length, over-estimated; for if once the conditions while the springing monad is not longer requisite for development of life de novo than one three-thousandth of an inch. in an organic fluid were ascertained, it The germs of these naturally bear some would be but one step further to imitate proportion to the size of their parents, those conditions in a manufactured fluid of and, consequently, the minute particles of known composition, and thus to gain some protoplasm which constitute the spores of conception of the way in which the first the calycine monad were some ten times germs of life may have originated on the as heavy as those of the other, and had earth. The theory of evolution would nearly all fallen and impregnated the fluid thus be complete at one end of the scale in the open basins before the covered ves- of being, and would receive a confirmasels were exposed. Mr. Dallinger put the tion of its truth which "none of our enematter to a further test. There is one mies would be able to gainsay or to remonad, the "uninflagellate" form, upon sist." which many of his observations had been The needful conditions for the spontamade; this in its adult state is about one neous development of life in boiled orfour-thousandth or one forty-five-hundredth ganic fluids are, according to Dr. Bastian, of an inch in length, and its spores are so the neutrality or slight alkalinity of the small as actually to be invisible with the fluid, or its maintenance at a tolerably high highest powers of the microscope. Dust temperature (115°-120° F.). He placed from a dried cake containing these spores his putrescible fluid (urine) in glass retorts, was mixed with some containing the com- into the necks of which he introduced a paratively gigantic calycine form, and the small sealed glass tube drawn out to a fine former experiment repeated. It was point and containing enough potash solufound that nearly all the calycine germs tion to neutralize the fluid, the potash hayhad fallen in twenty-four hours, all in forty-ing been previously heated to the tempertwo hours, for vessels exposed after the lapse of the last-named time contained not a single calycine monad, while every drop taken from them swarmed with the little uninflagellate form.

Mr. Dallinger has thus shown most conclusively that whenever a putrid infusion dries up there will be found a powdery mass containing spores which every breath of air will diffuse far and wide, and that some of these spores are so minute as to require two days to fall a few inches in a perfectly still atmosphere, so that the dis

ature of boiling water. After the introduction of the potash tube the retort and its contents were subjected for some minutes to the boiling temperature; the neck of the vessel was sealed during ebullition, and, after cooling, the potash was liberated by a shake sufficiently violent to break the capillary tube.

Under these circumstances Dr. Bastian found that in every case the fluid swarmed

* Proceedings of the Royal Society, 1876, vol. xxv., No. 172.

with bacteria after a longer or shorter | more affected by the temperature of 280° time; while no organisms were developed than by that of 212°; the putrescible fluid

if it remained acid, or if an excess of alkali had been added. Even under these latter circumstances, however, a copious development of bacteria was insured by keeping the fluid at a temperature of

122°.

was only boiled, under the ordinary atmospheric pressure, for five minutes, so that its composition could have been in no way altered, and yet the results obtained were, without exception, negative.

In Professor Tyndall's experiments the same course was adopted, except for the fact that the potash was heated only to 220° F. instead of 280°. Again the results were negative. Professor Tyndall, as usual, brings forward a "cloud of witnesses to prove his position, and says: "The experiments have already extended to one hundred and five instances, not one of which shows the least countenance to the doctrine of spontaneous generation."

Similar results have been obtained in

This is Dr. Bastian's case. But it will be observed that he failed to "mak sicker" in two important points: in the first place there was no proof that the fluids in question would not have developed bacteria without the addition of the potash; and, secondly, the potash was heated only to the temperature of boiling water, a temperature which, though amply sufficient to kill adult bacteria, has been proved, in many cases, to leave their germs unslain. It became essential, then, to repeat the experiments, allowing the fluids to stand sufficiently long, before adding potash, to make it tolerably certain that no organisms would be developed without the addition of the alkali, and to heat the potash to a temperature consider-perature above that prescribed by his ably above the boiling-point of water, so as to insure the complete destruction of the most enduring microphyte germs.

Experiments with these necessary precautions have lately been made by Professor Tyndall and Dr. W. Roberts, of Manchester, and their results seem to demonstrate, conclusively enough, the fallacy of Dr. Bastian's conclusions.

*

Dr. Roberts's experiments were conducted in the same manner as Dr. Bastian's, with one or two important modifications. In the first place the tube containing the proper quantity of potash for neutralization of the fluid was heated, in an oil bath, to a temperature of 280° F., 68° above the boiling-point of water; secondly, after the flask containing the boiled fluid with its contained potash tube had been hermetically sealed- of course during ebullition it was allowed to stand in a warm place for a fortnight, and thus prove its complete sterility. The potash tube was then broken, and the flask exposed to a temperature of 115°, and afterwards to one of 122°; that is, the fluid was exposed to the very conditions which, according to Dr. Bastian, are most potent in inducing spontaneous generation. Nevertheless every one of the flasks was found to be absolutely sterile. It must be observed that not one of the essential conditions was altered-potash is no

176.

France by M. Pasteur, and once more there seemed to be some promise of a settlement of the difficulty, when Dr. Bastian communicated to the French Academy the results of further experiments in which he had heated his potash to a tem

opponents and for a longer time, and, under these circumstances, he always obtained a copious development of bacteria.

Thus, then, the matter now stands with regard to this particular experiment, and the question seems to have become one of experimental ability between the upholders of the two opposing views. There are, however, certain facts recently brought forward by Professor Tyndall, which throw a very important light upon the possible cause of such extraordinary discrepancies.

It is a well-known fact that dried peas resist the action of boiling water for a much longer time than green peas — that in fact, the latter are reduced to a pulp in a space of time hardly sufficient to soften the former. Professor Tyndall † found that an infusion of old hay was much more difficult to sterilize than one of fresh hay, and that, while a few minutes' boiling sufficed to kill all germs in the latter, those contained in hay a year or two old resisted the action of heat for a very long time. He naturally concluded from this that the almost infinitely minute germs of microphytes may, in just the same manner as peas, become dried and hardened, and so able to oppose a long and obstinate resistance to the action of heat.

Loc. cit., p. 457.

↑ "Preliminary Note on the Development of OrProceedings of the Royal Society, vol. xxv., No. ganisms in Organic Infusions." Proceedings of the Royal Society, vol. xxv., No. 177.

Assuming, then, as it seems one is bound to do, that germs may and do undergo this excessive induration, one is able to form some conception of the difficulty of sterilizing a fluid in which, as is certainly the case in very many instances, veteran germs occur, and to appreciate the ingenuity with which Professor Tyndall has overcome the difficulty. He finds that frequent applications of a low degree of heat, applied at intervals, have a far greater sterilizing effect than a single application of a very high temperature.

that the retinas of all animals, instead of being white or greyish, as was supposed, were of a beautiful purple-red hue. Boll supposed that this color was destroyed during life by strong light and restored by darkness, and that it invariably disappeared, forever, a few seconds after death.

Since the publication of Boll's results, the subject has been investigated in great detail by Kühne,* who has arrived at conclusions the importance of which can hardly be too highly estimated. He found, first of all, that although the sight-purple A given fluid may contain germs of all (Sehpurpur) disappears within half a ages. If this fluid is boiled for a consid- minute after death in bright sunlight, yet erable period, all those of recent forma- that in gas-light it remains unaltered for tion will be killed at once, while those of twenty to thirty minutes, and in the dark, considerable age will only be just suffi- or when exposed only to the yellow light ciently softened to enable them to germi- of the sodium flame, for twenty-four to nate subsequently. If, on the other hand, forty-eight hours after the time, in fact, the fluid is first heated for a short time at which decomposition has set in. The and a fraction of a second is often suffi- color, moreover, exists only in the layer of cient - the recent germs will be killed, rods and cones, and although discharged and those a degree older so softened, that, by high temperature and by certain reafter a period of latency, they are ready agents, it remains unaffected by others, to germinate. Heat now applied for a such as common salt, alum, and glycerine, short time will kill these, and fit a third and is also unaltered when the retina is set for growth; and the same course may spread on a glass plate of course, in be adopted for successive crops, until yellow light-and allowed to undergo even the hardest and driest germ is killed. complete desiccation. Furthermore, when It was found that a fluid which was not a retina was spread out on glass, partly rendered barren by boiling for an hour covered by strips of tinfoil, and then exwas completely sterilized by this process, posed to light, it was found that the otheralthough never heated up to the boiling-wise bleached membrane retained its beaupoint, and although the whole time of tiful purple color wherever it had been heating did not amount to five minutes; protected from the action of light by the and even the infusions which had given tinfoil. In other words, there was imProfessor Tyndall most trouble were, pressed upon it a positive photograph of without exception, rendered permanently the strips. barren.

Many years ago an ingenious tale appeared in one of the magazines, the hero of which had a theory to the effect that the last object seen by a dying person was imprinted on the retina, and could, by suitable means, be photographed, and so preserved. His researches on this subject and his final success were detailed with great appearance of truth, and in the end he discovered the murderer of his sister by recognizing in a chance-met stranger the original of the portrait he had, years before, obtained from the eye of the victim. It is curious how prophetic this seemingly wild fable has turned out to be of a wonderful discovery made within the last few weeks.

A short time since Franz Boll observed

"On Heat as a Germicide when Discontinuously Applied." Read before the Royal Society in February.

It was now necessary to decide the question, How is the sight-purple renewed in the living animal after being bleached by light? The retina from one eye of a frog was removed and placed on a glass plate; an equatorial section was made of the other eye, and its posterior half was exposed to light, under the same conditions as the removed retina, until the latter was completely bleached. The second retina, still in its natural relations to the other coats of the eye, but presumably with its color discharged, was then taken into the sodium chamber, removed, placed on glass, and again brought into ordinary daylight. The purple colour was found to be perfectly restored. From another eye the retina was removed in such a way that some black fibres of the underlying choroid coat still adhered to it; it was then

Zur Photochemie, der Netzhaut." Gelesen in der Sitzung des naturhistorisch-medicinischen Vereins zu Heidelberg den 5 Januar, 1877.

fined. It was found also, as might have been expected, that a better image was obtained from the eye of a rabbit just killed than from one actually living, it being difficult in the latter case to overcome the regenerating action of the choroid on the sight-purple.

spread out on glass and exposed to light. I was accurately photographed - the panes The bleaching effect was less marked white, the crossbars red and sharply dewhen the choroid was left. Still more instructive is an experiment in which a portion of the retina was removed from its natural position until bleached, and then carefully put back, so as to be once more in contact with the choroid; when removed after a few minutes it was found that the sight-purple was completely renewed. It is thus proved that the restoration of the sensitive pigment is the special function of the choroid, the hexagonal cells of which, extending for a short distance between the rods and cones, continually sensitize the latter, as they become bleached by light.

It follows from this that, as Kühne observes in a subsequent paper,* normal vision is only possible while a constant balance exists between the bleaching of the rods by light and the purpurogenous action of the retinal epithelium. If, therefore, this balance were destroyed by a prolonged exposure to light, it should be possible to obtain a permanent optograph of a luminous object; and this Kühne now set himself to accomplish, devoting his attention to the eyes of mammals, in which the purple-forming function of the choroid ceases a few minutes after death.

A rabbit was fixed at a short distance (1.5 metre) from a square hole, of thirty centimetres in the side, in a window-shutter; its head was covered for a short interval with a black cloth, the cloth was removed, and the eye exposed to the light of midday for three minutes. The animal was then instantly beheaded, the eye removed in a chamber lighted by the sodium flame, and placed in a solution of alum. On the second day the retina was removed, and was found to exhibit, on a rose-red ground, a white image about one square millimetre in size, almost quadrate in shape, and with its edges sharp as if drawn by a ruler!

Naturally Kühne was not satisfied with this single experiment, decisive as it was, but a week after its publication brought out a third communication, in which even more beautiful and astonishing results are described.† A rabbit was treated in the same manner as the last, except that it was placed a short distance from an entire window, and not a hole in the shutter: in this case the whole image of the window

"Vorläufige Mittheilung über optographische Versuche." Centralblatt für die med. Wissenschaften, 18772 No. 3.

t Zweite Mittheilung über Optographie." Centralblatt, 1877, No. 4.

Lastly, Kühne tried the simplest method of optography: the head of a rabbit was cut off, and, without any preparation, held for ten minutes under the middle of a large skylight. After the usual treatment with alum, the retina was examined, and on it was seen the perfectly sharp image of the skylight, with every pane and crossbar accurately reproduced, and, at some distance, a smaller image of the second skylight of the room, the light from which of course fell obliquely into the eye.

To summarize -the essential conditions of vision are essentially photographic: the purple layer of rods and cones is altogether analogous to a sensitized plate, the color of which is discharged by light, but, during life, immediately renewed by the layer of epithelial cells in contact with it. And thus a great stride has been made in bringing the mysterious processes of life within the grasp of ordinary chemico-physical laws. Much yet remains to be done; the realm of things settled is still but an

816

with the little tinkling bell continually | ing for him, arrested till he should rejoin calling her to one thing or another, to it, to carry the wounded child to the matins or even-song, to "meditation," to hospital. He had left those mysterious this service or that, to choir practice, to glories of life, day after day and week carried a after week, to go and ask for little Emmy. dinner and tea and recreation tumult of fancies about with her, which How wonderful this was! The devotion no one, except perhaps Sister Mary Jane, of Sister Mary Jane, the loving-kindness guessed. Oswald would have stood aghast of Miss Cherry, faded before such an excould he have seen into that little ocean ample; for they had not the world at their of excited feeling, where the waves rose feet as this young paladin evidently had. higher and higher as the hours went on, and sometimes a swelling tide almost swept the thinker herself away-though indeed he would have been so unable to understand it that the inspection would How probably have taught him little. easily he took all this, which was so tremendous to her! and that not only because of the difference between man and woman, but because of the fundamental was difference in temperament, which greater still. Agnes had known but little that was lovely or pleasant in her life. Her rectory home was neither; her father and mother and brothers and sisters were all vulgar and commonplace, struggling for existence, and for such privileges as it contained, one against another, and against the world, each grumbling at the indulgences the other managed to secure. The parish and its poor and its rich, who were not much more attractive - had been all the world she had known; and the only beings who had crossed her horizon, who were not struggling like her own people, in the sordid race of existence, to get something, whatever it might be, were the sisters in the "house," and such a gentle retired person as Miss Cherry, who was not fighting for anything, who was ready to yield to any one, and whose mild existence was evidently not pervaded by that constant recollection of self which filled up all the life of the others. This was what had brought the visionary girl into the "house," which was sordid, too, in its details, though not in its spirit. Then there had been suddenly presented to her, just as she settled down to the work of the house, an image of something new, something more spontaneous, more easy in generosity, more noble in liberality than anything she had ever encountered. What did it matter that this, type of nobleness was a handsome young man? Visionary Agnes, in the daring of her youth, saw no harm, but rather a beautiful fitness, in the fact that this revelation of the ideal should have all that was best in externals as well He had as in more important things. stopped short-no doubt with all the brilliant world, which she did not know, wait

This was how the first chapter of the story came about. It opened her eyes (Agnes thought) to nobleness undreamed of, and for the first few weeks the universe itself had grown more bright to her. Could it be possible, then, that in "the world " itself, which the sisters had abjured in that splendid glorious "society" which even ascetic books spoke of as something too full of entrancements and seductions to be resisted by any but the most heroic, there were still opportu nities of living the highest unselfish life, to the glory of God and the comfort of man? When Agnes found that this ideal hero of hers had thoughts less exalted in his bosom, that so small a motive as the wish to see herself and talk to her had something to do with his devotion to the orphan, her visionary mind received a shock. Probably, had Oswald's enthusi asm been for another, she would have been permanently disquieted by the discovery; but there is something strangely Such conciliatory in the fact that it is one's self who is admired and followed. trivial emotions detract from the perfection of an ideal character; but still it is a much more easy thing to forgive your own lover than any one else's. And the more he sought her, the more Agnes's heart, in spite of herself, inclined towards the man who could be thus moved. The ideal stole away, but so insensibly, in rose-colored clouds, that she had not discovered the departure of her first admiration and wonder before something else stole in. It was not all goodness, nobleness, Chris i in charity, perhaps, that moved him; but what was it? Love, which in its way is divine too. Only after this altogether new influence had made itself felt did doubts appear, making a chaos in her mind. Were his sentiments as true as she had first thought? Was it right to counterfeit goodness, even in the name of love? Was not, after all, the life of the sisters, the life of sacrifice, more noble than the other smiling life, of which he was the emblem? Was it not a mean thing to go back from that, and all one's high thoughts of it, to the common romance of a story-book?