The dynamics of living matter dynamicsofliving1906loeb Year: 1906 GENERAL PHYSICAL CONSTITUTION OF LIVING MATTER 31 cannot be used as an unequivocal answer to our question, inasmuch as the possibihty exists that in later stages of segmentation the different cells undergo different chemical changes, whereby they no longer remain equal in quality. If we raise the question why such a limit exists in regard to the divisibihty of living matter, the answer is possibly given by Boveri's observation that the unsegmented egg of the sea urchin {Strongylocentrotus lividus) possesses three different l
The dynamics of living matter dynamicsofliving1906loeb Year: 1906 GENERAL PHYSICAL CONSTITUTION OF LIVING MATTER 31 cannot be used as an unequivocal answer to our question, inasmuch as the possibihty exists that in later stages of segmentation the different cells undergo different chemical changes, whereby they no longer remain equal in quality. If we raise the question why such a limit exists in regard to the divisibihty of living matter, the answer is possibly given by Boveri's observation that the unsegmented egg of the sea urchin {Strongylocentrotus lividus) possesses three different layers.* It is possible that these three layers contain chemically different material, and that only those fragments of an egg are capable of development which contain material of each of the three layers. If this be correct, it will certainly not suffice to mix the chemical con- stituents of the egg in order to produce the phenomena of development; but we must pro- fig. 6.—after boveri. vide for a definite arrangement or structure of Structure of the unfertilized ' ^ egg 01 a sea urchin. The this material. We shall see later on that this contents of the egg are , . , I 111- divided into three dis- structure may be very simple and capable 01 tinct layers. a physicochemical definition. The limits of divisibility seem therefore to depend upon the physical structure of the cells or organs. These limits vary for different organisms and cells. The smallest piece of a sea-urchin egg that can reach the plu- teus stage is still visible with the naked eye, and is therefore consider- ably larger than bacteria or many algae, which also may be capable of division. 2. Foam Structures and Emulsions Living matter seen through the microscope invariably offers the same characteristic appearance which has caused biologists to desig- nate it with one general term; namely, protoplasm. Yet the common physical fea;tures of living 'protoplasm' are still a matter of contro- versy. Some authors mainta
Size: 1414px × 1414px
Photo credit: © Bookend / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: archive, book, drawing, historical, history, illustration, image, page, picture, print, reference, vintage
