Prochaskalt next produced an excellent trea tise on muscle, in which he explained, with great clearness, the figure, size, and solidity of the elementary fibre, and the appearances of the fibrilla into which it divides. lie fell into the en-or, however, of confounding the trans verse markings in the intervals of the discs, with other creasings or flexuositics which never exist in the living body. but continually pre sent themselves, in the dead fibre, from me chanical causes. All these he attributed to lateral pressure made on the fibre and fibrilla by vessels, nerves, and areolar tissue, which he erroneously imagined to penetrate the inte rior of the fibre. Prochaska injected muscle with great success," and found the Vessels so numerous that he was induced to believe con traction to depend on distension of the vessels, throwing the fibrillae into zigzags.
Foutaina,t a few years afterwards, gave a much more accurate account of the fibre than had previously appeared, and one remarkable for its simplicity. According to him the ele mentary fibre consists of fibrilla, marked at equal distances by dark lines, which by their lateral apposition occasion the appearance of cross stria. Hence he styled the fibre a primitive fiiscirillus. By this term, which has been generally adopted, undue importance is attributed to the longitudinal cleavage, for the elementary fibre may as justly be called a pile as a bundle. It is not, however, in strictness, either one or the other.
In the period that has elapsed since Fon tana's description was published, up to the last few years, no real addition has been made to our knowledge, and so discredited or for gotten, at least in this country, were the labours of the authors already enumerated, that the anatomy of the muscular fibre was taken up as a new inquiry in 1818 by Sir Everard Home and Mr. Bauer.] The latter very excellent observer must have been deceived by the im perfection of his glasses, which do not seem to have been adapted to so minute a structure, for his results, as published by Sir F.. home, have had the effect of retarding rather than of advancing our knowledge, by raising doubts as to the credibility of any conclusions founded on microscopical research. In 1832, Dr. Hodgkin and Mr. Lister§ re-discovered the transverse markings on the elementary fibre of voluntary muscle and of the heart, and pointed out, as Muys and Fontana had done, that their presence was a character by which this could be distinguished from the fibre of the uterus, bladder, &c., which latter they con, sequently denied to be muscular. Since thee, many inquirers, both in this country and abroad, have taken up the subject with proved instruments.
Among those who have arrived at conclu sions similar to those of Fontana may be men tioned the names of Lauth, Schwann, and hlenle. Others, however, have entertained very opposite and, as I believe, erroneous view s of the composition of the fibre. Mandl con ceives the cross markings to be produced by a spiral thread of areolar tissue investing the fibre, and Mr. Skey* describes them as an external structure, independent of the fibrilla', which he believes to be arranged in band-like sets around a glutinous substance in the axis of the fibre. Ficinust falls into the old error of Prochaska, of imagining the striae to be the result of minute flexures of the fibrillae, and, Ike him, he confounds with them the secondary flexures of the whole fibre. hence, says he, the appearance of globules or particles is false, and only exists during contraction. Other opinions still I have had occasion to allude to in the course of the article M VSCI-F, which, as before remarked, is founded on observations which have been now two years before the public.: All the best observers are agreed as to the existence of certain appearances, and the dis crepancies we encounter in the interpretation of them ought not to bring discredit on all researches of this sort. They place, indeed,
in a strong light the difficulty of the inquiry, and the necessity for repeated, varied, and un biassed observation, with the best instruments we can command But we are too familiar with conflicting and even opposite statements concerning visible facts, occurring daily under the eyes of every one, to suppose it possible that any kind of investigation will ever be free from those causes of error, which lie in man's nature, in his own microcosm, and the effects of which can only be neutralized by the common consent of numerous independent observers. As for those difficulties, whatever they may be, which are inherent in the nature of the subject, we cannot doubt that they will be, in due time, appreciated and overcome.
Some of the opinions concerning the nature of contraction, entertained by the earlier ob servers, have been already mentioned; another, which seems to have been grafted on the doc trine of the vital spirits, was, that these spirits were directed into the fibres and distended them, thus causing them to tumify and shorten. Accordingly, some (as Robert Hooke and Cowper) considered each fibre or fibrilla to be hollow; which need not excite surprise, when we find the great Mascagni§ believing each to be a lymphatic vessel. The first hint of another very noted hypothesis is to be found in the Memoirs of the French Academy. 1724 :— L'Abbe de Molikes there says,11 " Les fibres charnues qui s'etendent scion la longueur du muscle, et dont he raccourcissement fait son action, se divisent en tin grand nombre de petites fibres de naerne nature longitudinales aussi, et qui sont liees les unes aux autres par des filets nerveux transversaux disposes le long des fibres de distance en distance. De plus, les petites fibres charnues ne sont pas droites, mars pliees en zigszags, dont les angles se trouvent aux endroits, oU sont his filets trans versaux." Hales* examined the abdominal muscles of small living frogs, and saw them thrown into zigzags during contraction, as he imagined ; but he mistook the uncontracted for contracted fibres, as I have explained.t Pre vost and Dumas, at a later period,: described the same zigzag flexure of the fibres during contraction, and further imagined it to be an electrical effect produced by the passage of the nerves across them at their angles of flexure. This doctrine was too captivating not to obtain very general credence, especially as it seemed to fall in with a notion, at that time very cur rent among speculative physiologists, that the nervous influence is a form of electricity. But its validity has of late begun to be questioned ; Professor Owen,§ in small filarim and in a spe cies of vesicularia, observed a fact opposed to it, viz. the bulging of the (unstriped) fibres near their centre, without their falling out of the straight line, in contraction. A similar fact was observed in the case of the (unstriped) muscles of the Polypifera, by Dr. A. Farre;11 and Dr. Allen Thomson,ll on repeating the experiment of Hales and Prevost on the Frog, " observed single fibres continuing in contrac tion, and being simply shortened, and not fall ing into zigzag plicre ; and he was led to sus pect, from this and other circumstances, that the zigzag arrangement was not produced until after the act of contraction had ceased." M. Lauth, after a careful investigation, concludes** that a fibre may shorten with or without zigzag inflection. Such, I believe, was the state of this question in 1840, when I published the observations,tf on part of which the account of the nature of contraction, given in the pre sent article, is principally based. In the fol lowing year I added:: a note, on the appear ances met with in human muscle ruptured by tetanic spasm, and which seemed to me to prove that the conclusions I had previously drawn from the phenomena of the rigor mortis were true as regards the act of contraction, as it occurs in the Tiring body.