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us unapt to receive it. We remember observing, that, when the fear of our importing the yellow-fever was prevalent, there was really little danger, unless we could also import American constitutions; and this idea was confirmed by our having seen this fever, as described by the American physicians, in this country, but in a mild form, and not infectious. It could be evidently traced to the sea-ports, and very nearly to American ships.
Dr. Heberden seems to think the plague infectious yet the tenor of his observations shows that it is rather communicated from the air, than from infection itself. A pestilential fever, he remarks, often precedes and is absorbed in the pestilential epidemic; nor are any very clear marks of distinction laid down. We may indeed observe, that, during the prevalence of all epidemics, every other febrile disease disappears: and this is not peculiar to the plague; for the local affection sometimes attends other fevers. Yet, on the whole, the buboes are, if not exclusively peculiar to, yet more particularly observable in, the pestilential disease; and there are many other marks of its being a distinct disorder. Our late expedition to Egypt has familiarised our practitioners to it; and they were little afraid of infection, when the disease was properly known. That it is not a putrid disease, is very evident; it is rather a highly asthenic fever, in which the patient sinks through debility, with scarcely any sign of putrid fluids. We have, however, still our epidemics, which occasionally distress us, and are at times fatal, though not putrid. Thus the late influenza, the grippe of the French, was a highly debilitating disease, and perilous from the sinking of the constitution: putrid peripneumonies have also occasionally become frequent in particular districts, and been often fatal: others might be added. Did the plague occasionally recur, these would be swallowed in its vortex ; but at present they appear distinct. We mean not, however, to put them on a footing with the plague. Even the late influenza, we believe, never destroyed, in the whole kingdom, five hundred persons, if we except those who, tottering over the grave, would have fallen on the slightest attack of an indigestion or a common cold; and if, in any district of this kingdom, an epidemic become fatal to a dozen persons, the greatest alarm ensues. On the whole, we have now little to dread from epidemics, and nothing from the plague-Suave mari magno, &c.
We promised some observations on the construction of bills of mortality, and the improper use which has been made of them; but our article has extended so far, that we can allot but a few words to this subject. From an error in their construction, or other causes, the mortality has appeared too great; and the calculations resulting from them have hence failed. In
societies in favour of survivorship, too few have died. This, in part, arises from the calculations having been made for great cities, while the societies have admitted, indiscriminately, the inhabitants of the country. If the population had not been rated too high, the error would have been still greater. At present,' we believe the deaths in large cities are considerably exaggerated, and those in the country not properly appreciated. If we were to hazard a calculation, from the average of many cities and country-towns now before us, we should be disposed to assert, that, in the whole of England, not one in forty-five dies annually. In general, however, the average has been taken much lower, and the event is the destruction of the hopes of numerous individuals. We have before us the calcuIation of many tontines. After about twenty years, not one quarter of the mortality, promised by numerous bills, has taken place. In one instance, three only have died, when twentyfive was the number expected.
ART. III.--Transactions of the Linnean Society. Volume VI. 4to. 21. 2s. Boards. White. 1802.
WE will not delay our account of the labours of this respectable society by any formal introduction; and indeed the present volume offers no subject of preface on our part. We shall therefore follow the articles, as usual, in their order.
I. A Dissertation on two natural Genera hitherto confounded under the Name of Mantis. By Anthony Augustus Henry Lichtenstein, D.D. F. M. L.S. Translated from the German by Thomas Young, M. D. F. R.S. and L.S.'
Entomology must be allowed to be yet in its infancy; and each step, when carefully undertaken, and with proper views, will be of service to its progress. The separation of those species which feed on plants, and have no falciform fore-feet, (their legs being all formed for running) from the genus mantis, was first suggested by Stoll, a naturalist of great acuteness, but without education. He anticipated the genera of Fabricius; for he systematised, it is said, nearly in the same manner, without any communication with that naturalist: but, though he died before the work of Fabricius was published, he might have been informed of its substance. The coincidence is too striking to be accidental. The discrimination between the mantis and the new genus phasma, or spectre, selected from the species formerly arranged under the genus mantis, we shall
1. Antenne setaceous with long- 1. Antennæ filiform.
MANTIS. "Fangschrecke." 2. The head nodding, heartshaped, with jaws and palpi.
3. Two large prominent eyes on the sides.
4. In most species two clear stemmata between the roots of the antennæ.
5. The thorax narrow, on the back
6. Six legs, the foremost with
Their modes of life equally differ. The former live on vegetable food, lay their eggs, like grasshoppers, in the earth, which the female penetrates with a small style, of an ensiform figure, covered with three leaflets found on the last division of the abdomen; while the latter feed on animals, which they catch and carry to their mouths with their falciform hands, and fix their eggs on twigs, straws, &c. in regular rows or masses. The more minute differences are too long for our notice. Of each genus we have a distinct character; and the species are well discriminated, with the necessary synonyms. About seventeen new species are added; and drawings of the P. filiforme hecticum, and Ortmanni, with the M. filum, contribute to illustrate the descriptions. Some little difficulties arise, from the males and females of each species not being discriminated; and it is remarked that the first fifteen mantes of Fabricius are phasmata, so that this naturalist seems to have noticed a striking distinction.
II. The Botanical History of the Genus Ehrharta. By Olof Swartz, M.D. F. M. L. S.'
The grass arranged under this genus was first discovered at the Cape, by Thunberg, and described and delineated by him in the Swedish Memoirs for 177. In the same year, it was adopted among the Nova Graminum Genera, by the younger Linnæus; and a grass was described in the Journal de Physique, under the title of trochera striata, nearly related to the Ehrharta. Some time afterwards, three other species were deCRIT. REV. Vol. 38. August, 1803.
scribed and delineated by the president of the Linnæan society, the first of which was descried by Sonnerat, at the Cape, in 1776, and the latter had appeared in the Linnæan supplement, with the appellation of aira capensis. From the similarity of this genus with the melicæ, our author was anxious to rescue those species which might have been confounded with them; and we find three species of melicæ, and two of airæ, now added to the genus Ehrhata by an examination of Thunberg's own herbarium. These are carefully described, and the distinguishing parts accurately represented. The trochera striata is added.
III. Account of a microscopical Investigation of several Species of Pollen, with Remarks and Questions on the Structure and Use of that Part of Vegetables. By Luke Howard, Esq. of Plastow in Essex.'
It was well known that the pollen-the dust separated from the extremities of the antheræ-when wetted, would explode, and throw out minute grains, supposed to be the substance that impregnated the female organs, in order to the production of the new vegetable. Mr. Howard has not added greatly to this knowledge, though he has made some progress. He concludes, with sufficient accuracy,
1. That each grain of pollen in the anther is an organic body, variously constructed in various species, and containing
a Vessels or pores capable of imbibing water, of distending thereby and contracting again when it quits them; in which particulars they resemble sponge, &c.
b A parenchymia, consisting of some substance (of greater specific gravity than water, and insoluble therein), which is emitted with a greater or less degree of force when the stimulus of alcohol is applied to the absorbent vessels. This substance is either in part soluble in alcohol, or the grains contain
'c An essential oil or resin, to which they owe their colour and odour.
2. That there exists in the grains of pollen, in a very eminent degree, that property of vegetables called irritability, which they are capable of retaining for a certain time after separation from the anther.
That alcohol is the proper stimulus by which this irritability may be excited, and the texture of the pollen in some manner developed in consequence thereof. I prefer this method of accounting for the appearances that take place when the pollen is immersed in spirit to another that might be supposed on chemical principles, being assured, that any one who has once inspected the process will be satisfied that something more than mere solution or chemical decomposition takes place therein, and that the vital principle of the pollen is the chief agent.
The liquor from the tube of the pistil and the solution of sugar were, indeed, found to bring on the evolution of the pollen of cactus Flugel, in a slower manner than spirit; but when we consider how
speedily such matters pass into the vinous state, it seems possible that both of these might contain alcohol. Yet, it is also possible that something common to this latter substance, with the saccharine matter it is producible from, may be the real exciting cause.
The existence of absorbent vessels in the pollen is proved by the change of form, increased transparency, and great distension produced by the water. It is remarkable, that complete saturation usually brings the grains near to a spherical shape, however remote from it their original one.' P. 70.
The existence of the parenchyma is evinced by various arguments; and the explosion will explain the different motions previous to the discharge. The particles of starch seem, from examination, to resemble pollen in its structure; and all vegetable fæcula seems of a similar nature. The potatoe appears only an assemblage of the grains of fæcula; and, when boiled or roasted, so as to become mealy, the water is absorbed in these grains, as in the pollen when moistened. Some hints, to assist the vegetable physiologist in pursuit of this investigation, are subjoined.
IV. Observations on Aphides, chiefly intended to show that they are the principal Cause of Blights in Plants, and the sole Cause of the Honey-Dew. By the late Mr. William Curtis, F.L.S.'
This very curious and entertaining paper explains the natural history of these little insects, which very generally occasion blights. Two very singular circumstances in their œconomy deserve notice; the one is, that they are occasionally oviparous or viviparous, as the cold is more or less intense; and the other, that the same impregnation extends its effects to perhaps more than twenty succeeding generations, without requiring to be repeated. The honey-dew is the excrement of these insects. Water does not injure them, and tobacco-smoke only is noxious. Their great enemies are the coccinella or lady-bird, the ichneumon fly, and a species of musca, thence called aphidivora. The following description of the destruction of the aphis by the ichneumon is highly curious.
Another most formidable enemy to the aphis is a very minute, black and slender ichneumon fly, the ichneumon aphidum of Linnæus. The manner in which this insect proves so destructive to the aphis is different from that of the lady-bird. The female ichneumon, of which numbers may be found where aphides are in plenty, settles on a stalk, or leaf, more or less covered with them, marches slowly over their bodies, feeling with its antenne as it proceeds for one of a suitable size and age; which having discovered, it pushes forward its body, or abdomen, in an incurved state, and with a fine instrument at its extremity, invisible to the naked eye, punctures, and deposits an egg in, the body of the aphis; which having done, it proceeds, and lays an egg in a similar way in the bodies of many others. The egg thus deposited quickly hatches, and becomes a small larva, or maggot, which