File:Contributions from the Botanical Laboratory, vol. 7 (1892) (20500082970).jpg

Title: Contributions from the Botanical Laboratory, vol. 7
Identifier: contributionsfro07univ (find matches)
Year: 1892 (1890s)
Authors: University of Pennsylvania. Botanical Laboratory
Subjects: Botany; Botany
Publisher: Philadelphia : University of Pennsylvania Press
Contributing Library: Penn State University
Digitizing Sponsor: Lyrasis Members and Sloan Foundation

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Reprinted from The American Natitralist, Vol. LXIII, September-October, 1929. THE CONTKACTILITY OF PROTOPLASM^ PROFESSOR WILLIAM SEIFRIZ University of Pennsylvania Contractility, elasticity, cohesiveness, rigidity and tensile strength are closely related properties of living matter which owe their existence to a specific type of structure. Polarity and conductance are other proper- ties of protoplasm which, though of quite a different nature from those first enumerated, depend upon the same specific structure. It is my purpose to give experimental proof of the presence of these physical properties in protoplasm and then to consider the character and arrangement of the structural units which account for these properties. I have already presented to this society^ a general idea of a structure which meets the requirements of an elastic yet fluid system. It is my wish to-day to carry this con- cept still further and to give a more detailed picture of the architectural background of protoplasm. The earliest investigators of living matter realized that the substratum of life has certain properties which are more characteristic of solids than of liquids. Pfeifer deserves credit for making the first quantitative measure- ment of one of these properties. He performed the in- genious experiment of tying minute weights to the end of a freely hanging strand of the plasmodium of the slime-mould Chondrioderma and ascertaining the load which the protoplasmic thread would support. From this he calculated the tensile strength or, as he expressed it, the cohesive force of the protoplasm. (This was found to average 50 mgr per sq. mm; 3.5 mgr actual weight on a strand measuring 0.3 mm in diameter.) The modern technique of microdissection (termed Micrurgie" by Peterfi) has given us another way to No. 688) CONTRACTILITY OF PROTOPLASM 411 << 1 Address given at the Symposium on The Neuromuscular System, American Society of Naturalists, New York City, December 29, 1928. 2 Amer. Nat., 60: 124 (1926). 410 demonstrate, and to measure with accuracy, certain of the physical properties of protoplasm. Stretching the living substance between microneedles will convince any one of its extraordinarily high elasticity and tensile strength. Those workers Avho repeatedly emphasize a liquid nature of protoplasm should go through the ex- perience of placing microneedles in a red blood corpuscle and stretching this corpuscle to its elastic limit (Fig.
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