accidents that may prevent the spermatozoa from meeting with them. The true "spores" of the Algae are really the "germ-cells, "which seem to be commonly fertilized, like the ova of fishes, after they have been set free from their conceptacles. But almost all Alge propagate also by detached gemmæ, which often constitute what is known as a second form of fructification, and which, when they are carried about by ciliary action, are known as "zoospores ;" and this is the only method of propagation at present known to occur in the Ulvæ and some other tribes. There can be little doubt, however, from the analogy of the tribes to which these are most closely allied, that an act of conjugation or impregnation takes place at some period or other of their development.

We may sum up our present knowledge of the true "act of generation" in plants as follows:-Its essential character everywhere consists in the union or mixture of the contents of two cells, the "sperm-cells" and the "germ-cells;" but this may take place after three modes. 1. In the simplest cellular plants, where every cell appears to possess the same endowments, so that there is no kind of specialization of function, the generative act consists in the " conjugation" of two cells, between which no difference whatever can be traced. In what may be considered the lowest forms of this process, both cells discharge their contents, and the new body, or sporangium, is formed between them by the mixture of their endochromes; so that neither cell of the pair can be considered in the light of a "sperm-cell" or a "germ-cell." We have here the exact converse of the process of multiplication by fission, already described; for as, in the latter, one cell divides itself into two equal halves, between which no difference can be traced, so in the act of conjugation, two cells, apparently similar, reunite, and form but a single new cell between them. That union, however, seems to develope a new force, in virtue of which the process of subdivision may continue until that force be expended. In the higher forms of this process there is still the same mixture of endochromes by the actual rupture of the cell-walls, and the escape of their contents; but this mixture takes place, and the sporangium is formed (as in many of the Desmideæ and Zygnemata), within one of the conjugating cells, which must thus be regarded as the "germ-cell." We have here an indication of the specialization that is apparent in those more complex fabrics, in which certain cells are set apart for the performance of the act of generation, and in which the "sperm-cells" and "germ-cells" are quite distinct in their endowments. 2. In the higher Algæ, and in most, if not all, other Cryptogamia, the process is effected by the agency of moving filaments, resembling the spermatozoa of animals, which bring the essential part of the contents of the "sperm-cells" into such a relation with the "germ-cells," that a transudation may take place from the former to the latter, without any rupture of the walls of the latter. Of this process, the true germ is the result. This germ may be cast at once upon its own resources, as in the Algæ; or it may be nourished by its parent structure, as in the Ferns. It may at once proceed to the development of the new plant, similar to that from which it sprang, as it seems to do in the Alga; or it may develope itself into a body containing a mass of gemmæ, each of which may produce a new plant, as in the Hepaticæ and Mosses; or it may spring from the temporary portion of the plant, and evolve the whole permanent fabric, as in Ferns, the latter producing gemmæ

from which a new generative apparatus arises.* In none of these cases does the parent appear to furnish that accumulation of nutritive matter for the development of the product of the germ-cell, which, when included in a common envelope with it, would constitute a true "seed." 3. In the Phanerogamia, the "sperm-cell," or pollen-grain, does not evolve selfmoving filaments, as in the Cryptogamia, but puts forth long tubes, which convey its fertilizing contents to the "germ-cell" after a different fashion, still, however, fulfilling the same essential purpose. We adverted, on a former occasion, to the concurrence of nearly all the most recent and trustworthy observers, in the denial of Schleiden's assertion that the embryo is formed within the extremity of the pollen-tube; the fact appearing to be rather, that the embryonic vesicle is formed within the embryo-sac without any actual penetration of the pollen-tube, and that the mixture of the contents of the "sperm-cell" and "germ-cell" is accomplished by transudation through the membrane of the pollen-tube and that of the embryonic vesicle. The germ-cell is here imbedded in a mass of nutritious matter, which, with the embryo, constitutes the "seed;" and it is upon this store that the young plant subsists during the early stages of its development. The first leafy parts which are put forth,the cotyledons,-have a merely temporary function, being evidently destined to obtain and elaborate the materials required for the evolution of the more permanent organs; and we might regard the subsequently developed parts as originating from them by gemmation.†

We have thus endeavoured, so far as our limited space would allow, to place before our readers some of the most interesting results of those recent investigations in physiological botany, which bear most closely upon animal physiology; and we cannot but think that it must be as apparent to them as it is to ourselves, that these two departments of science are so closely related, that they will be most successfully pursued in concert, and with a mutual good understanding between their respective votaries. We feel ourselves called upon to protest most strongly against the denunciations which Professor Schleiden has thought it proper to utter against all those, who labour at drawing closer the bonds of union between these two great kingdoms of organized nature. We are no friends to the vague and superficial analogies, which men, who had no true insight into their relation, have amused themselves with drawing; but we do contend that real and fundamental analogies exist, which are clearly to be recognised by those who possess a sufficiently comprehensive knowledge of the phenomena, and a sufficient amount of philosophic sagacity, to be able to

• This last would be reckoned by the disciples of Steenstrup as a case of "alternation of generations;" the true Fern, originating from the fertilized germ, being one generation; and the primary frond, originating from a gemma, being in their apprehension a second generation. We shall return hereafter (Art. VIII) to the discussion whether the term "generation" can be rightly applied in this or any similar case of gemmiparous reproduction, which comes more properly, in our apprehension, under the term "development;" and shall at present only remark, that the case fully confirms our general doctrine (Vol. I, p. 205), that in every instance of such alternation, it exists really between the products of sexual and non-sexual reproduction, and that it never occurs between the products of the true generative process, which invariably repeat the same type.

+ Professor E. Forbes carries his idea of the succession of generations in flowering-plants to such an extent, as to regard the cotyledons as forming one generation, the first true leaf a second generation, and so on. According to this doctrine, the germinal membrane of the animal embryo, which is the distinct analogue of the cotyledons, and the chick which is developed through its means, constitute two distinct generations, instead of being the successive phases of the evolution of one and the same individual.

distinguish the essential from the accidental, the real from the formal. The simple fact that the animal, like the plant, is evolved from a single cell, and that even in the most perfect condition of each, all its functions are but manifestations of different kinds of cell-life, should at once indicate that the most comprehensive principles of vital action must be common to both, and that the differences in their structure must have relation to the difference of the conditions under which they are to exist, and the difference of the results they are to evolve. The "idea" of a plant is that of a being possessed of the power of combining certain inorganic elements into organic compounds, and of building up, at the expense of these, an organized fabric, which shall afford materials for the nutrition of animals; but this being is not endowed with sentient attributes or locomotive powers; it is usually fixed to one spot from the time its germ first begins to develope itself, and its whole life consists in formation and reproduction. On the other hand, the "idea" of an animal is that of a being possessed of sentient existence, but that existence is (in our present state at least) dependent upon, or inseparably connected with, an organized structure: powers of formation there must be, as in plants; but these are exercised upon organic compounds, supplied directly or indirectly by the vegetable kingdom; and the animal must be endowed with locomotive faculties to go in search of these, or with some means of bringing them within its reach : and the whole apparatus of nutrition seems destined simply to form and to maintain that of animal life, by which the conscious existence is brought into relation with the world around, so as to receive impressions from it, and in its turn to act upon it; whilst that of reproduction secures its renewal. Considering that the plant and the animal have the same startingpoint, the single cell,-we might naturally expect that the "act of generation," of which that cell is the result, should be the one whose performance in the two kingdoms might display the greatest resemblance; and we think that no one who appreciates the details we have given can fail to perceive how remarkably this is the case. It is curious, however, to observe, that in no single tribe of plants is the reproductive process performed on both sides after the pattern of that of animals; for whilst in the Cryptogamia the "sperm-cells" bear so strong a resemblance to those of animals, that they might be mistaken for them, the "germ-cell" is naked, instead of being inclosed within a yolk and yolk-bag; whilst in the Phanerogamia we find ovules resembling the ova of animals in all essential particulars, but fertilized by a different development of the sperm-cell.

Notwithstanding that we have felt called upon, in our discussion of every one of the subjects upon which we have touched, to express our dissent from Professor Schleiden's views, and to condemn the spirit and temper in which he has put them forth, we should not be doing justice to his labours if we did not also repeat our statement, that by his elucidation of a vast number of other topics, which it does not fall within our province to discuss, he has contributed most successfully as well as diligently to the advancement of botanical science. We regard the plan of his work, and the method of investigation on which it is based, as far superior to that of any other systematic treatise on the subject; and no one can rightly comprehend the present aspect of Botanical science, without a careful study of it.

ART. III.

De l'Infection Purulente, ou Pyoèmie. Par le Docteur C. SEDILLOT, Chirurgien principal des Armées, Membre correspondant de l'Institut de France, &c. &c. Avec Trois Planches coloriées.-Paris, 1849. 8vo, pp. 520.

On Purulent Infection, or Pyæmia. By Dr. C. SEDILLOT.

"PURULENT Infection," or, as it perhaps might be better rendered in our vernacular, "Poisoning by Pus," is the term adopted to indicate a train of symptoms which seem to be of much commoner occurrence in the Continental hospitals than in our own, or at all events to have attracted more attention there than here, having been somewhat vaguely set down among us as the general phenomena attendant upon some forms of phlebitis. It is true that some of our writers have suggested that the highly irritative character of the symptoms is probably due to the presence of pus in the blood, and that even the capillary phlebitis to which they have in some cases been referred, may be sometimes itself produced by a preliminary contamination of the blood by pus, although, in other instances, it is itself the starting point, and in either case keeps up a continued supply of the toxical agent. M. Sedillot lays down the proposition absolutely, that the symptoms described under the various names of purulent infection, purulent absorption, purulent diathesis, suppurative phlebitis, &c., are always produced by the admission of the pus-globule into the blood. That such entry of pus into the circulation is the usual cause of these, although not operating as M. Sedillot represents, may be admitted; but that it alone can give rise to them, we do not believe: for not only is such admission, under some of the circumstances mentioned by the author, somewhat problematical, and its exclusiveness waived by him in favour of putrid matters; but assemblages of symptoms having the greatest analogy to those described under the term purulent infection, are met with in cases wherein pus has had nothing to do with their production. Thus, for example, typhus fever, some forms of puerperal fever, erysipelas, &c., attended with the severest constitutional irritation, may be generated in the wards of hospitals under the influence of over-crowding and consequent vitiation of the air, the encombrement of the French, the ochlesis of Dr. Gregory. There can be little doubt that in these cases a subtile poisonous matter enters and ferments in the blood; and such explanation will apply to very many of the cases set down by Mr. Travers and his followers as originating in a primary affection of the nervous system. Farther, a practitioner will go to puerperal patients, one after another, all perhaps favorably situated as regards hygienic circumstances, conveying to them at his fingers' ends, or even in his habiliments, a poison far more subtile than the pus-globule, and yet capable of inducing a train of symptoms just as frightful as those set forth by our author. It is quite recently that a remarkable mortality amongst the puerperal women at the Vienna Hospital was traced to the fact of their being attended by students in the intervals of their dissections, the deaths being far less frequent among those attended by the midwives. The publication of this fact forcibly called to our mind the large proportion of puerperal fevers we met with during our pupillage, compared

8-IV.

.4

to the experience of after life. But we are here perhaps combating a shadow; for the author in point of fact does not regard pus as a poison, but as a local irritant. Admitted into the blood, he says, it exerts no direct action on that fluid whatever, and only becomes mischievous when it becomes detained in the capillary vessels of the lungs or other organs, exciting the irritative symptoms characteristic of the affection, in consequence of the impediment it offers to the due performance of their functions, and to the attempts made at its elimination. We may reserve any remarks we may have to make upon this doctrine until we have allowed him to state his views more fully; and as the detection of the pus-globule in the blood is considered by him to be highly important in prognosis, as evidencing the formation of secondary abscesses, we may first refer to the conclusions upon this point to which he has been led by attentive and prolonged examinations, made under a great variety of circumstances. According to these, the pus-globules are two or three times larger than those of the blood, their contour is more regular, their granular or nipple-like projections are more distinct, their transparency is less, their specific gravity is greater, and the tendency they have to adhere to bodies prevents their being carried along in the current as are the blood-globules. The white globules of the blood, however, have a certain resemblance to those of pus, but exist in far fewer numbers, and are detected with much greater difficulty. In all doubtful cases the author has, as a means of comparison, made contemporary examinations of healthy blood and of blood to which pus has been added. M. Lebert has furnished him with a note upon these distinctions, in which he observes that, however easy it may be to confound the two by a superficial examination with a low power, the differences become obvious if a power of from 500 to 800 diameters be employed.

"The dimensions are different, that of the pus-globule varying from 1 to millimeter, that of the white globule from 0 to 1, a sixth or a fifth smaller. The colour of the pus-globule is slightly yellowish, that of the white globule a dead white, without any trace of yellow. The form of the pus-globule is spherical, while that of the white one is much more flattened, being at most lenticular, and never spherical. The surface of the pus-globule is roughened compared with the smooth surface of the white globule. A marked difference is generally seen in the nuclei as exhibited in both by means of acetic acid. Those of the pus-globules are much larger, varying from to millimeter, and exhibit in their interior a regular well defined cavity, while the white globule furnishes scarcely other than very small puniliform nuclei of from 0 to millimeter, rather resembling nucleoli or fatty granules." (p. 269.)

In regard to any effect produced upon the appearance of the bloodglobule by the introduction of pus, Dr. Sedillot is very sceptical; and he entirely derides the idea of the conversion of the one into the other, having always found the two remain distinct after commingling them experimentally. A multitude of examinations have proved to him that changes in the shape and appearance of the blood-globule are quite as frequent in healthy blood as in blood containing pus; while in cases in which the circulation has abounded in pus-globules, the shape of the blood-globule has been found quite normal. Some of the supposed changes are due to the imperfect manner in which the microscopic observations have been conducted.