From fibrous contractions

I. All the fibrous contractions of animal bodies originate from the fenforium, and refolve themfclves into four clafles, cor-refpondent with the four powers or motions of the fenforium above deferibed, and from which they have their caufation. 

From the AV node, the electrical impulse spreads through the AV bundle or the bundle of His. This portion of the conduction system penetrates the fibrous tissue separating the atria from the ventricles and enters the interventricular septum where it divides into the left and right bundle branches. The bundle branches travel down the septum toward the apex of the heart and then reverse direction, traveling back toward the atria along the outer ventricle walls. This route of conduction of the impulse facilitates ejection of blood from the ventricles. If the impulse were to be conducted directly from the atria to the ventricles, the ventricular contraction would begin at the top of the chambers and proceed downward toward the apex. This would trap the blood at the bottom of the chambers. Instead, the wave of ventricular electrical stimulation and, therefore, contraction moves from the apex of the heart toward the top of the chambers where the semilunar valves are located and ejection takes place. 

The magnitude of the two thermally induced contractions is quite uniform among samples of newborn rat corneum, but considerable variation is encountered with human corneum, particularly for the 196 °C contraction. The contraction values for human corneum samples varied from 1 to 5% but were quite consistent for any given subject. The increased magnitude for this contraction in some human specimens could indicate a higher degree of orientation of the crystalline fibrous material 11). 

Recently, still more fibrous proteins have been isolated from muscle tropomyosin, discovered by Bailey in 1946 (1946a), and paramyosin, discovered by Bear in 1944. It seems certain that neither of these proteins participates in the contraction process (Bailey 1948 Astbury 1948 Schmitt et at., 1947). 

Uniform clear films of a epidermin, freed from the non-fibrous 0 component, were chosen of thickness about 2/i. Pieces were mounted on stainless steel frames, the initial area being about 1X1 cm. After wetting in water these films were stretched a little more than three times their initial length, which is about the limit that can be achieved safely with such delicate films. According to Fig. 13 extensions of this order give nearly the maximum contraction on release. The infrared spectra of such a film with 200% extension are shown in Fig. 14A for the ranges 3600-2600 cm.-i and 1750-1450 cm.- ... 

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