ZOOLOGY. 393 



blood, which is about seven-eighths water. The lungs being in partial 

 vacuo, and having a temperature at least thirty-five degrees above that re- 

 quired in a complete vacuum to change water into vapor, a portion of the 

 water contained in the blood becomes steam. The volume of the blood thus 

 enlarged exerts a specific force. The valves on the right side of the heart 

 close against it, while those on the left open, to give it free passage. Thus, 

 according to this theory, is generated the primum mobile the true motive 

 power, which first produces, and afterwards keeps up the circulation of the 

 blood. In the mean time the mechanism of the heart not only determines 

 by its valves the course of the blood current, but equalizes its flow, and adds, 

 by the mechanical force of its stroke, to the chemical power. But without 

 this power, however free the heart may be to act, as in drowning, hanging, 

 etc., life can be but a few moments sustained. 



This theory has received the support and sanction of some of the leading 

 men in the medical profession of this country, and as such is worthy of 

 a place in any record of the progress of science. 



ACTION OF LIGHT ON MUSCULAR FIBRES. 



At a meeting of the English Royal Society, during the past year, M. 

 Brown Se'quard presented a communication on the action of light on mus- 

 cular fibres, independent of the influence of the nerves. That light is capa- 

 ble of producing such an effect, was mentioned by several of the old anato- 

 mists, but later authorities repudiated the idea, and the subject remained un- 

 noticed. The experiments, however, of M. Se'quard, prove that some portions 

 of muscular fibre the iris of the eye for example are affected by light, 

 independently of any reflex action of the nerves, thereby confirming former 

 experiences. The effect is produced by the illuminating rays only the 

 chemical and heat-rays remain neutral. And not least remarkable is the 

 fact, that the iris of an eel showed itself susceptible of the excitement six- 

 teen days after the eyes were removed from the creature's head. So far as 

 is yet known, this muscle is the only one on which light thus takes effect; 

 and henceforth, the statement that " muscular fibre may be stimulated with- 

 out the intervention of nerves/' will have to be received among the truths of 

 physiology. 



