B L I S T E R- F L Y B L O O D. 



517 



conceived would have the effect of producing of itself 

 a swarm of aphides. We will not, in this place, enter 

 into the inquiry, whether the wind in question might 

 not have a twofold influence both upon the insects' 

 eggs and the leaves of the plant, nor will we stop to 

 deride whether the saccharine and viscid juice be a 

 morbid secretion of the leaves, or merely the excre- 

 mentitious matter of the aphides, the eggs of which 

 had been alone influenced by the action of the wind, 

 and hatched, our object in this article being chiefly 

 directed to an explanation of the sudden appearance 

 of insects, termed blight, and which we trust that we 

 have succeeded in giving, by stripping the subject of 

 the marvellous, and tracing its causes to the well- 

 known rules of insect life. We will only, in con- 

 clusion, remark, with reference to the latter part of 

 our observations, that so completely are the aphides 

 dependent upon atmospheric peculiarities, that in the 

 present remarkable season, although these insects 

 swarmed to so great an extent in the spring months, 

 as entirely to stop the growth of the roses, yet, 

 throughout the summer, and up to the present time 

 (September), we have not been able to meet with 

 specimens sufficient to prosecute experiments upon 

 their habits and economy. 



BLISTER-FLY. See CANTHARIS. 

 BLITE. An English weed, the Amarantus bill inn 

 of Linnieus. A small inconspicuous plant, usually 

 found growing on dunghills. 



BLOOD, in p/ij/siotogi/, the vital fluid of animals, 

 or that by which they, in all their varieties, are dis- 

 tinguished from the other kingdom of organised 

 beings, the vegetable tribes. It is written that "the 

 blood is the life," and though tin's must be regarded 

 as a figurative expression, as must also those other 

 cases in which "blood" is used as the designation for 

 different tribes or families of man, or for different 

 races of other animals, yet there is no animal life 

 without blood ; the nature and action of this fluid 

 are intimately connected with the development of 

 life, and also of the living organisation and the quan- 

 tity of living action ; so that the blood is more typical 

 of life and living action than any other part of the 

 animal. 



It may be considered as the primary or rudimental 

 matter, out of which all the other parts of an animal 

 are formed at the first, and the grand means by 

 which they are kept in repair ; and as we have no 

 other abstract notion of life, taken in so wide a sense 

 as to include all living creatures, but motion, or to 

 speak more correctly self-motion, so we find that the 

 energy of life is always in proportion to the degree 

 of motion in the blood. The act of turning into 

 blood is, thus, the specific act of animalisation, the 

 ultimate part of the process of assimilating ; and in 

 the formed animal, after it begins to subsist upon 

 food of whatever kind, there is no changing of any 

 sort of aliment into any one structure or part of the 

 animal, without first turning that substance into 

 blood. Nor does it appear that there is in the mature 

 animal, whatever may be its age, any means by which 

 the food, even if it is the blood of another animal, 

 can be converted into blood of the feeder, without a 

 direct mixture with the blood as already formed. 

 Some account of the progress and changes of the 

 food, from its first entering the alimentary canal to 

 the final discharge of the chyle into the vein by the 

 thoracic duct, will be found in the article ASSIMILA- 

 TION. But, as there stated, the prepared food carried 



to the vein by this duct, is not only not blood, but 

 unfit for mingling with that blood which goes directly 

 to the nourishment and support of the animal frame, 

 till it has been first sent to the lungs and undergone 

 the action of the air in respiration there ; and, though 

 so far as we know, the experiment has not been made, 

 it is highly probable that if the contents of the tho- 

 racic duct were mixed directly with the blood in the 

 systematic arteries, or that which goes directly to the 

 different parts of the animal, it would contaminate 

 that fluid, or become a poison. 



In all cases in which animal poisons animal, the 

 blood is the part more immediately affected by the 

 virus. The direct poisons which are secreted by 

 healthy animals are deadly only to the blood, taken 

 into it by direct injection or by absorption which 

 probably takes place to some extent throughout the 

 whole venous system. There are some animals, and 

 animal substances which, taken into the stomach act 

 as poisons ; but those which do so when killed in a 

 healthy state, and not subjected to corruption after- 

 wards, are comparatively few ; and the appearances 

 which the body presents when so poisoned, very much 

 resemble those which are consequent upon death 

 from animal virus, whether the venom of animals 

 naturally poisonous, or the morbid matter of disease 

 or putrescence. It is the blood which is tainted, and 

 the primary appearances an- spots and discolorations 

 on the surface of the body, which if the morbid matter 

 is not too powerful in its operation, and the body is 

 capable of re-acting, often proceed to suppuration, 

 in a manner similar to those diseases which are un- 

 derstood to arise from inoculation. 



Poisons from mineral substances, and also some of 

 those from vegetable ones, give rise to similar appear- 

 ances ; but these arc, in most cases, if not invariably, 

 secondary, and induced by a disease in the blood, 

 consequent upon the specific action of the mineral or 

 the vegetable poison. The specific action of the mine- 

 ral poison is, as we might naturally expect, analogous 

 to the ordinary action of mineral upon mineral, that 

 is, it is chemical, it corrodes, or decomposes ; and up 

 to a certain point, the action of even the most deadly 

 mineral poison may be not only harmless, but posi- 

 tively salutary. Arsenic itself is, in skilful hands, a 

 very valuable medicine ; and so are iodine and prussic 

 acid, though these last are to be resrarded as vegetable 

 substances rather than minerals. 



The specific action of vegetable poisons, considered 

 strictly as such, is on the sensibility of the animal, or 

 as it is usually expressed, on " the nervous system ;" 

 though as the vegetable is not so much removed from 

 the mineral as the animal is, many vegetable poisons 

 have also a corrosive or, as it may be termed, a 

 mineral or chemical action. These poisons, like the 

 mineral ones, are harmless or medicinal, up to a cer- 

 tain point ; and those deadly effects may, in most 

 cases, if not in all, be said to be secondary. But, as 

 they are still organic substances, or the products of 

 organisation, they approximate more nearly to direct 

 poisons acting upon the vital fluid than the mineral 

 ones, though their chemical effects arc, for the same 

 reason, not so violent. Hence the common notion 

 that active or drastic vegetable medicines are safer 

 than mineral ones of the same power, is both a preju- 

 dice and an error; and one which, in the hands of 

 ignorant and impudent empirics (and they cannot be 

 the one without being the other,) is productive of 

 incalculable mischief to the credulous. 



