Page:Popular Science Monthly Volume 19.djvu/427

Rh diagrams to show the interactions of the nervous and muscular parts, as it is now proved that they take place.

We have here no space for the details of the book, but may refer to one of the most delicate and interesting of the machines employed, which is a device for the electric measurement of the muscle-pulsation. By its use the infinitesimal periods of time consumed in these pulsations are magnified and represented side by side in a wavy line, so that their durations can be compared and measured by a standard. The continued strain of a muscle is shown to be a chain of these tiny pulsations which decline steadily in strength as each pulsation exhausts a certain amount of material corresponding to the carbon removed from its place under the steam-boiler by combustion. The modern view that the power generated by muscle is due to the hydro-carbonaceous matter oxidized, instead of the nitrogeneous element of muscular structure, is clearly brought out.

It has long been a question in what way the nerves are mechanically or structurally related to the muscles, or what is the nature of the ultimate connection. Of course this was a microscopical problem upon which further light was constantly thrown as the instruments reached higher powers, and observers became more skilled in their use, and more experienced in guarding against errors. As was natural, different views were entertained by different able observers, and, as was equally natural, sharp controversies followed. How the case stands at present may be gathered from the following statement from Chapter XV: "If we trace the course of the nerve within the muscle, we find that the separate fibers, which enter the muscle in a connected bundle, separate, run among the muscle-fibers, and spread throughout the muscle. It then appears that the single nerve-fibers divide, and this explains the fact that each muscle fiber is eventually provided with a nerve fiber—long nerve-fibers even with two—although the number of nerve-fibers which enter the muscle is generally much less than the number of the muscle-fibers which compose the muscle. Till the nerve approaches the muscle-fiber, it retains its three characteristic marks—the neurilemma, medullary sheath, and axis-cylinder. When near the muscle-fiber the nerve suddenly becomes thinner, loses the medullary sheath, then again thickens, the neurilemma coalesces with the sarcolemma of the muscle-fiber, and the axis-cylinder passes directly into a structure which lies within the sarcolemma pouch, in immediate contact with the actual muscle-substance, and is called the terminal nerve-plate." There are some differences here in different classes of animals, but "the essential fact is the same in all cases: the nerve passes into direct contact with the muscle-substance. All observers are now agreed on this point. Uncertainty prevails only as to the further nature of the terminal plate."

no subject which interests so many people and interests them so deeply is so little studied or understood as the history of the Bible. In these three kingdoms there are every Sunday between fifty and sixty thousand clergymen of various religious bodies discoursing upon it, a very much larger number of persons teaching it in Sunday-schools and day-schools, an overwhelming majority of the population reading it, more or less, and looking to it as the guide of faith and practice. Yet not one man in a thousand, even in the educated classes, knows anything about the respective dates of the different books of the Bible, the mode in which they were preserved and received into the canon of Scripture, or the views entertained by scholars as to their authorship. This ignorance is deepest and most widespread as regards the Old Testament. Wonderful progress has been made during the last fifty years in the criticism of the numerous writings which make it up. It is not too much to say that we have gained more knowledge on the subject within that period than all the labors of all Biblical scholars succeeded in amassing during the two thousand years that preceded. Yet the bulk of the English cultivated public, which learned at college at least all that is known about the Servian Constitution and the Twelve Tables, which has a fair idea