Volume 5

The elements of materia medica. Comprehending the natural history, preparation, properties, composition, effects and uses of medicines / [Jonathan Pereira].

Pereira, Jonathan, 1804-1853.

Date:: 1839-1840

Credit: The elements of materia medica. Comprehending the natural history, preparation, properties, composition, effects and uses of medicines / [Jonathan Pereira]. Source: Wellcome Collection.

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$. the mechanical impulse fails, or the activity of the poison is exhausted — before, in the latter case, it reaches the second animal.” A remarkable error pervades the whole train of reasoning adopted by — Messrs. Morgan and Addison, and vitiates some of their conclusions. — They assume that Magendie considers actual contact with the brain as— essential for the operation of the Upas poison, (see pp. 42, 43, 47, 49, &c. of the Essay.) This assumption, however, is not correct. “In 1809,” says Magendie (Formulaire, 8™° éd. p. i.) “I laid before the first class of the French Institute, a series of experiments which had conducted me to an unexpected result, namely, that an entire family of plants (the bitter | Strychnos) have the singular property of powerfully exciting the spinal marrow, without involving, except indirectly, the functions of the brain.” Now, this being Magendie’s opinion, it is evident that, in the experiment performed by Messrs. Morgan and Addison, the blood sent from the carotid artery of the poisoned animal to the brain of the sound one could only reach the spinal marrow by the usual route of the circulation ; that is, it must be returned by the jugular veins to the heart, from thence to the lungs, back again to the heart, from thence into the aorta, and then distributed through the system. Now it is not too much to suppose that, during this transit, some portion of the poison might be decomposed or thrown out of the system before it could arrive at the spinal marrow ; and even if this were not the case, this organ could only receive a small quan- tity of the poison contained in the system, namely, that sent by the verte- bral to the spinal arteries. Hence we ought to expect that a poison thrown into the arteries will operate less powerfully than when thrown into the veins, unless it be into the arteries supplying the parts on which the poison acts. Moreover, as an anonymous reviewer has observed (Lond. Med. and Phys. Jour. vol. \xiii.) it is to be recollected that as the carotid artery, in its healthy state, is little more than one-fourth of the calibre of the vessels carrying blood directly to the brain, consequently the dog not inoculated was subject to the influence of one-fourth only of the quantity of the poison which was conveyed to the brain alone of the inoculated animal. Furthermore I would add, that it is not too much to suppose that the circulation of the blood through the tube would not be so free as through the artery. How DO MEDICINES AND POISONS WHICH HAVE ENTERED THE BLOOD- VESSELS AFFECT DISTANT ORGANS ?—Viewing the question theoretically, we see three ways by one or more of which remote parts might be scon- ceived to become affected after medicinal globules have passed into the blood. , 2 1. By modifying or altering the properties of the blood, and thereby unfitting it for carrying on the functions of the body.—Although no facts are known which can be regarded as absolutely proving that the action of medicines or poisons is primarily on the blood, yet none I believe are inconsistent with such a notion in all cases, while several strongly favour it: and it has been justly observed by Andral (Treatise on Pathological Anatomy, translated by Drs. Townsend and West, vol. i. p. 642), that “as the blood nourishes the solids, and as without its presence they cannot support life, the state of the solids cannot but be influenced by the state of the blood.” In the first place, it must be admitted that in many diseases the pro- perties of the. blood are altered, and in some cases these alterations often$