734 



connexion of the current with the lungs was severed by a ligature 

 placed on the vein between the insertion of the wire and the heart, 

 the current was instantly reversed, passing up the vein and returning 

 by the artery. The same reverse current was indicated when the 

 wires were inserted into portions of the blood-vessels which had been 

 isolated, each by two ligatures, placed the one above and the other 

 below the insertion of the M'ires. A similar effect was also obtained, 

 as long as the blood continued to coagulate, when the two kinds of 

 blood were drawn from the blood-vessels into separate cups, and 

 brought into connexion with the galvanometer ; the blood in the cups 

 being connected together by the ends of a piece of copper or of a 

 strip of muscle dipping into each. 



Several experiments are related, tending to prove that the power 

 which fluids, differing chemically from each other in however great 

 a degree, were supposed to possess of acting chemically upon the 

 copper wire, and thus generating currents, had been greatly exag- 

 gerated ; and that much which had been attributed to this cause de- 

 served rather to be ascribed to the polar forces, which the fluids had 

 a tendency to assume, being discharged through the copper as a 

 conductor, since the same efiect was produced when platinum was 

 used, and in an appreciable degree even when no metal was in con- 

 tact with those artificial compounds, cotton moistened with water 

 being only used to make the different connexions with the fluids. 



The author then traces the course of the blood in the foetus, show- 

 ing that the blood passes in it, throughout the body, in the direction 

 wholly from artery to vein ; the upper half constituting one segment, 

 and the lower half of the body the other segment of the circle ; and 

 pointed out that, thus far, there was no antagonism of forces, and 

 therefore no power of generating a galvanic current, which he indi- 

 cated was supplied by the smaller circle, through the placenta, join- 

 ing the larger circle at the vena cava, and leaving it at the hypo- 

 gastric arteries; the smaller circle inducing the current in the larger, 

 in the same manner as the larger circle in the adult may be supposed 

 to induce lesser secondary circles, as the hepatic, &c. 



The author then dilates on the importance of the galvanic current 

 in physiological and pathological inquiry ; pointing out the peculiar 

 significance of the fact of the reverse current being established as 

 soon as the direct current is impeded ; the systemic capillaries being 

 endowed with the power of generating a force exactly the reverse to 

 that set up in the lungs ; the rapidity of the circulation thus being, 

 cceteris paribus, the measure of the excess of the primary force over 

 the resistance. He infers, that the galvanism found in the muscles 

 owes its origin to the opposed condition of the blood in the capillary 

 network which supplies each ; the anastomoses of the arterial capil- 

 laries with each other increasing their galvanic surface, while their 

 limited anastomoses with the veins supply the conditions necessary 

 for the passive cuiTent. The office of conductors, for the active dis- 

 charge of the accumulated force, is assigned to the nerves of the 

 voluntary muscles ; the author believing that the circuit by which 

 this is effected is, in them, prolonged up to and from the nervou? 



