are, however, of value, not so much as affording a measure of the infecting activity of the liquid as in their application to the question at issue. They furnish strong additional evidence in support of the doctrine that contagium consists of particles. They show that, whatever may be the degree of dilution, the local effect produced, provided that it is produced at all, is always the same. In other words, the difference between the effect of inoculating extremely diluted liquid and that of inoculating the liquid itself, without any addition of water, does not manifest itself as might be expected in the size of the individual pustule or pustules produced, nor even in the character of the secondary eruption, or the constitutional disturbance which accompanies it. The difference lies entirely in the numerical relation of successes to failures. If successful, inoculation with a liquid containing a myriadth of infecting juice communicates the disease as completely as the pure liquid itself. The fact is not only perfectly consistent with the notion that contagium is particulate, but is in itself a necessary consequence of its being so. If, on the other hand, contagium were soluble, it could not be explained, for in that case each of the 10,000 drops in which the one drop had been dissolved would be equally active. Assuming it to be particulate, it follows that the myriad particles which were before distributed in one drop are scattered through 10,000 drops. And inasmuch as there is nothing excepting the influence of currents to ensure the equal distribution of the particles, it is clear that in some regions of the liquid the distance from each other will be greater, in others less. Consequently, when a trace of the liquid thus feebly impregnated with contagium is taken up on the point of the lancet, the chance that the little drop will or will not contain particles may be stated numerically by the fraction which expresses the degree of dilution. And here it is of importance to notice that the same explanation applies to a fact of common observation with respect to all of those diseases which are contagious at a distance. The question is frequently asked, How does it happen that a person may be exposed every day for many months to the contagion of typhus with immunity, and yet be eventually attacked, without any change whatever being made, either in his own condition, or in that of the infected media by which he is surrounded.

"If contagium were gaseous, the fact would be inexplicable-as inexplicable, indeed, as the assertions of the homoeopathists. Assuming it to be insoluble and particulate, the question of mediate contagion must, like that of direct contagion, be one of chance."

Dr. Sanderson undoubtedly, at the end of his valuable essay on the physical properties of contagion, affords us strong arguments to prove that the contagious "principle" is neither soluble in water nor capable of assuming the form of vapour. It becomes, therefore, necessary, at the commencement of his second part on the organic forms which occur in infecting liquids, precisely to define the limits of the inquiry.

93-XLVII.

2

"The question has been commonly stated somewhat as follows: If contagium is alive, it may be so in one of two senses, either as a part of the living body which is the seat of the disease, or as in itself a living organized being inhabiting the diseased body. If it is not alive, its actions must be chemical.

"The distinction which this mode of stating the question implies between chemical on the one hand, and living on the other, if not entirely meaningless, is, at all events, too vague to be used for scientific purposes; for inasmuch as no vital function can be performed without chemical change, and as many chemical changes are constantly attended with vital manifestations, neither term can be applied to any process to the exclusion of the other. In short, the only character by which the living can be separated from the not living, is that of organic development; so that the question may be considered to lie between those who hold that the particles of contagium are living organisms, and those who attribute their infective properties to their chemical composition."

It must here be noted that our idea of development is based on our idea of the individual, and that separate cell life appears to go on in the dead as well as in the living subject. The totality of that number of structures we term the individual may be dead, yet separate cell life may exist in its component parts. Life is merely organisation or structure in action, and condition of development has nothing whatever to do with the matter. A living thing has been defined by Professor Owen as an "object which possesses such an internal cellular or cellulovascular structure as can receive fluid matter from without, and alter its nature and add it to the alterative structure.' "Development" is an accidental, not an essential character. There are cells which truly live, but do not pass through any stages of development.

The researches of Professor Hallier, of Jena, are commented on by Dr. B. Sanderson at great length. Professor Hallier considers that the organic forms which are met with in contagious fluids are analogous. He includes them under the general term Hefe, a vague word, which is understood to mean a form of fungus which consists of minute single cells, which reproduce themselves with extraordinary rapidity, exist in all substances, undergoing putrefaction or fermentation, and grow and multiply at the expense of those substances. They never lose their unicellular character, and cannot be said to have spores or mycelium, each individual cell being alike an organ of growth and an organ of reproduction.

The musk plant, the yeast plant, and the Sarcina are examples of acrite or protozoal forms. They may, according to Dr. Sanderson, be divided into two groups: one comprises the

ferment plants already mentioned, and the other containing those forms which are associated with the commencement of decomposition of the nitrogeneous compounds of which putrefaction is the continuation. The proof that these bodies are living organisms, and not mere particles of protoplasm, is because it is clearly ascertained that under certain conditions they elongate into rod-like bodies endowed with a peculiar progressive and oscillatory movement. So long as these bodies, which Béchamp and Sanderson call "Microzymes," are spheroidal, they are called Micrococci or Microspores. When they become staff-shaped they are termed Bacteridia or Bacteria. The generic names Schizomycetes (Nageli, De Bary), Vibrio, Bacterium, Zooglea, Nosema, Sarcina, and other terms, have been employed for these forms. Their precise zoological position cannot be ascertained until we know more of their development. Analogous forms known as Cryptococcus, Hormiscium, Arthrococcus, Oïdium, are known which merely represent the transformation of any of these forms from the circular into the elongated shape. Those for example in the cryptococcus of the yeast plant, when the liquid begins to turn acid, the cells become elongated, and begin to divide by transverse constriction. Hallier expresses this fact by saying that cryptococcus has undergone transformation into arthrococcus.

"Thus in the fermentation of beer the Cryptococcus Cerevisia is produced so long as the vinous fermentation continues, but as soon as air is allowed free access the cryptococcus cells bud out into cylindrical processes, which divide by transverse septa; and finally, if the acid fermentation ceases, giving way to putrefaction, micrococcus again appears, being formed, according to Hallier, by repeated division of the nuclei of the arthrococcus cells. Thus the series micrococcus, cryptococcus, arthrococcus, micrococcus, cryptococcus, and so on, may recur indefinitely, provided that the growing material be subjected in due order to the corresponding conditions, viz., putrefaction, vinous fermentation, acid fermentation, putrefaction, &c."

In fact, such terms as Arthrococcus or Cryptococcus merely represent various stages of the same organism.

Two questions are suggested by Dr. Sanderson, the one which relates to the connection which his discoveries bear to the theory of spontaneous generation being prudently dismissed by him in a few words. For the practical import of the discoveries of Pouchet or the speculations of Pasteur is simply nothing, and the pathologist has not to concern himself with the absolute genesis, but with the proximate causes and forms of development of the microzymes. The endless question of spontaneous generation may be set entirely apart, as it has no immediate

practical import of any kind, and though it has the fascination which attaches to all mysterious subjects, it may be passed over on the present occasion without any minute discussion. As Dr. Sanderson says, "It is agreed by all (without prejudice to the doctrine of spontaneous generation) that microzymes, like other organic forms, do as a rule originate from predecessors, that is to say, by reproduction." The modification of the omne vivum ex ovo theory here propounded is so mild as neither to offend the most ardent evolutionist nor the most fervid advocate of heterogenesis.

The researches of Professor Hallier, vague though they may be adjudged, will probably serve as the basis whence we may draw an enormously vast induction as to the future importance of the subject.

"The establishment of the doctrine that the microzymes of contagium are capable of developing to higher specific forms, and that they can be reproduced from them is the end and aim of all Professor Hallier's investigations. They can best be judged of by the examination of those instances in which the evidence is strongest, and is supported by the greatest number of facts; for one is more likely to form an accurate opinion of the value of the whole investigation by the sceptical scrutiny of one or two examples, than by a cursory examination of a greater number."

It is distinctly proved that in the alvine liquid of cholera "microzymes "exist of characters identical with the "micrococci" and "arthrococci" of the zoologists. Thus, Professor Klob of Vienna has made discoveries which we have already alluded to, and which indicate that the change from the spheroidal to the rod-like form has been observed in all the specimens which he has described, and which appear to consist not only of globular particles, but also of an interstitial jelly. M. Thomé, a botanist in Cologne, cultivated these jelly-like masses on wheaten bread moistened with lemon juice, and succeeded in obtaining a filamentous substance, which when submitted to Professor De Bary was considered by him to be "oïdium." In May, 1867, many months after the cessation of the epidemic, Hallier discovered in some alvine cholera liquid which had been obtained at Berlin, and preserved for examination, certain globular cysts, the contents of which subsequently swelled out into gelatinous masses similar to those found before in cholera liquids. By cultivating those microzymes in a suitable manner he produced from them in succession, first, other forms of ferment plants (Hefe), and eventually the same oïdium which Thomé had obtained directly from the cholera liquid. This cholera microzyme was afterwards cultivated on rice.

"In the course of the summer of 1867 some rice grains were

steeped with cholera liquid, and sown on suitable soil. The grains became infested throughout with mycelium, but germinated. The young rice plants, however, were weakly, and their leaves were stunted, while other grains, which had not been steeped, and were sown near the infected grains, grew to vigorous seedlings. The leaves of the sickly plants soon showed more distinct evidence of disease. A line of dark discoloration, extending from their bases to the extremities, indicated the presence of one of those fungi commonly known as smuts. On examination of the fructification it was found to present the characters of Urocystis.

"These experiments were suggested by a theory as to the origin of cholera, which may be stated as follows:-Cholera originates on the banks of the Ganges, where the rice plant abounds and flourishes. The contagium particles of cholera are manufactured in the cysts of a Urocystis, which is parasitic on the rice plant, by the conversion of the protoplasm they contain into microzymes, so that the same material which, when brought into contact with the germinating grain, produces Urocystis generates cholera when introduced into the intestine."

It is, however, to be noted that Dr. Sanderson points out that

"It is in the first place to be noticed that in the descriptions of all Professor Hallier's experiments, and particularly in the account he gives of this fundamental one, there is a strange neglect of details as to the precautions and methods employed. Thus nothing is said as to the use of any means for protecting the grains from impregnation with microzymes of other than choleraic origin, so that we are bound to assume that such microzymes were present."

The experiments on the rice grains also show that the epithelium which was contained in the fresh cholera liquid was beset with micrococcus in great quantity, in addition to which there were the cysts already referred to in a mature state. A liquid which thus contained both cyst and micrococci leaves us in a state of extreme doubt as to the value of the scientific conclusions which may be drawn, as it is surely quite as reasonable to suppose that the parasitic mycelium originated from sporidia as that it was produced by the germination of microzymes.

The time which has usually, as in the case of Professor Hallier's experiments, elapsed between the collection of the specimens and their examination is also an important factor of doubt.

"Thus the fact of the existence of cysts in the dejection of cholera rests on the examination of two specimens only, both of which have been already mentioned, viz. a bottle of alvine liquid collected in Berlin in 1866, and examined in 1867, and the quantity collected in Elberfeld in June of the latter year. The appearances observed in these two liquids unfortunately cannot be compared, for they are described only in the Berlin liquid. It is much to be regretted that