408 Royal Society. 



ployment of the author, living on his ordinary food, and working 

 at his usual employment. A strict examination was instituted into 

 the quantity and chemical constituents of the ingesta and egesta 

 during ten days ; at the end of which time he had gained one pound 

 in weight. He infers from the results of this experiment, that the 

 carbon and hydrogen contained in the food of animals, which enter 

 into combination with the respired oxygen, forming carbonic acid 

 and water, do not generate sufficient heat for the purposes of animal 

 life ; and that consequently there must be some other sources of 

 heat in the animal economy, one of which he believes to be the 

 secretion of carbon. 



" Electro-Physiological Researches. — Fourth Memoir. On the 

 Physiological Action of the Electric Current." By Charles Mat- 

 teucci. Communicated by Michael Faraday, Esq., LL.D., F.R.S. 



In the prosecution of his inquiries on the physiological action of 

 electric currents, the author found it necessary to employ an appa- 

 ratus, which was expressly made for him by M. Breguet, adapted 

 to the delicate appreciation of the intensity of the force of the mus- 

 cular contractions excited by those currents ; of which apparatus 

 he gives a minute description, illustrated by a drawing. He was 

 thus enabled to institute an exact comparison between the contrac- 

 tions caused by the direct, and those by the reverse currents, both 

 at the commencement and at the termination of their action. The 

 following are the general conclusions he deduces from the experi- 

 ments thus conducted. 



1. The passage of the electric current through a mixed nerve pro- 

 duces a variation in the excitability of the nerve, differing essen- 

 tially in degree, according to the direction of the current through 

 the nerve. This excitability is weakened and ultimately destroyed ; 

 and this takes place more or less rapidly according as the direct 

 current, that is, a current circulating through the nerve from the 

 centre to the periphery, is more or less intense. On the other hand, 

 by the passage of the same current in the contrary direction, that 

 is, from the periphery to the centre, or the inverse current, the ex- 

 citability is preserved and increased. 



2. The variations in the excitability of the nerve produced by 

 the passage of the current, tend to disappear more or less rapidly on 

 the current ceasing. If the nerve be taken from a living animal, or 

 from one in which life is but just extinct, so that its excitability is 

 very great, these variations last only as long as the current con- 

 tinues to circulate; while, if the nerve has already lost some of its 

 excitability, they survive the cessation of the current by a period 

 of from one to ten or fifteen seconds. 



3. If the same current be made to act upon a mixed nerve, the 

 contraction which occurs on the first moment of its introduction is 

 very different according to its direction ; the direct current always 

 occasioning a stronger contraction than that produced by the in- 

 verse current. 



" On Phlogiston and the Decomposition of Water." By W. F. 

 Stevenson, Esq., F.R.S. 



