The Biological Bulletin Volume 17 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1909 Excerpt: ...of the plasma-membrane. Essentially similar effects may result in many cases from moderate rise of temperature. Thus exposure of frog's muscle to temperatures approaching 400 for a short time produces the typical phenomenon known as heat-rigor, in which the muscle shortens and thickens while its substance undergoes complete coagulation and acquires a pronounced acid reaction. A closely similar change results when a muscle is immersed in a saturated solution of a lipoid-solvent like chloroform in an indifferent medium (e. g.t Ringer's solution). In both cases the changes in the muscle are associated with a loss of semi-permeability and of electrical polarization; and they are almost undoubtedly direct consequences of this since neither the moderate rise of temperature nor the presence of chloroform has by itself any such coagulative effect on the colloids composing the muscle substance; while loss of semipermeability, with consequent disturbance of chemical equilibrium and production of acids, may readily produce just such effects.1 Why such moderate heat should so profoundly alter the properties of the plasma-membrane is not evident at first sight; possibly the colloidal aggregation-state is the condition immediately influenced by the change of temperature; possibly the primary effect is a chemical one. The above are instances of artificially produced or pathological changes in permeability. Normal or functional changes in this property appear to be of frequent occurrence in living organisms. Thus there is highly conclusive evidence that the general process of stimulation is dependent on a temporary and reversible increase in permeability. Very clear indications of this kind are 1 Compare my former paper, American Journal of Physiology, 1908, XXII., pp. 81-...