September 1, 1922] 



SCIENCE 



237 



gives good hope that the public will have ex- 

 cellent scientific help in the promotion of the 

 national mineral industry. 



After the opening ceremony the president, 

 followed by the other guests, made a tour of 

 inspection of the library and of the museum. 

 H. T. Chang, 

 Peking, Acting Director 



July 17, 1922 



AGGLUTINATION AND TISSUE 

 FORMATION 



Foe a considerable number of years the prin- 

 ciple underlying our analysis of tissue forma- 

 tion — undertaken with the view of contributing 

 to a physiology of tissues in contradistinction 

 to a physiology of organs^ — was the sugges- 

 tion that primarily agglutination is the factor 

 which makes isolated cells join into a tissue, 

 and that this agglutination depends on a cer- 

 tain consistency of the outer layer of the cell 

 protoplasm-. In an analysis of tissue forma- 

 tion it was thus necessary to determine the 

 factors on which this consistency depends and 

 we showed that it is a quantitatively variable 

 factor, that this variability is a prerequisite 

 in amcBboid movement and that the same ag- 

 glutinability which determines tissue formation 

 is the cause of what we have called stereo- 

 tropism of tissue cells, their tendency to move 

 in contact with solid surfaces.- Tissue forma- 

 tion, stereotropism and amceboid movement are 

 therefore related phenomena, all depending on 

 a certain variability and regulation in the 

 consistency of the outer layer of the proto- 

 plasm. As a step in this investigation we pre- 

 ■ pared an experimental amoebocyte tissue which 

 consists of motile bloodcells of invertebrates 

 and which readily admits of an experimental 

 analysis of all these associated factors.^ The 

 basic laws of tissue formation must apply 



^Biological Bulletin, 1903, IV, 1301, Virchow's 

 ArcHv. 1903, CLXXIII; 135 Anatomical Ee- 

 oord 1912 VI, 109. 



^Washington University studies 1920, VIII, 3. 

 American Journ. Physiol. 1921, LVI, 140. 

 Science 1921, LIII, 261. 



sWashington University Studies, 1920. VIII. 

 3 Science 1919 L. 502. American Journal 

 Physiol. 1922, LX, 277. 



equally to the various kinds of growth, em- 

 bryonic, regenerative, -correlative and tumor 

 growth.* 



Tissues are primarily aggregates of agglu- 

 tinated cells. Secondarily certain differentia- 

 tions may occur which concern the individual 

 cells as well as the connections between these 

 cells. Elementary tissues and even structures 

 resembling particular tissues in certain re- 

 spects, can be produced from isolated amcebo- 

 cytes under conditions which we have described 

 in detail elsewhere. Under the influence of en- 

 vii'onmental changes the consistency of the 

 outer protoplasmic layer of these cells is 

 altered in such a way that it becomes sticky. 

 In this experimental tissue various processes 

 which occur in natural tissues can be imitated. 

 A state of the outer parts of the protoplasm 

 intermediate between liquid and solid is essen- 

 tial for tissue formation, because it insures 

 that degree of adhesiveness necessary for this 

 process. Agglutination is likewise the basic 

 factor, which insures the possibility of the 

 formation of paraplastic structures in which 

 the products of adjoining cells are united into 

 a homogeneous whole. 



We showed that the movements of tissue 

 cells take place in contact with surfaces which 

 are solid or approach the solid state, such as 

 fibres. We designated this mode of reaction 

 as stereotropism of tissue cells (1898), and 

 attributed to it a significant part, not only in 

 wound healing, but also in processes taking 

 place normally in the organism whenever 

 movements of tissue cells occur.'* This stereo- 

 tropism is apparent not only in normally mo- 

 tile cells, but even in cells which are normally 

 in a fixed condition but which are made to 

 move under conditions which imply a change in 

 environment; it is self-evident that this in- 

 cludes also those environmental changes which 

 take place during embryonal development. 

 We found that this stereotropic reaction can 



^Virchow's Archiv. 1903, CLXXIII, 135. 

 Journ. Med. Research, 1917, XXXII, 75, 1920, 

 XLI, 247. Journ. Cancer Research, 1920, V, 261. 

 Science, 1922, LV, No. 1410. 



sArehiv. f. Bntwickelungsmeeh. 1898, VI, 297. 

 1902, XIII, 487. Anatomical Record, 1912, VI, 

 109. M. S. Fleischer and Leo Loeb. Proc. Soc. 

 Exp. Biol, and Med., 1911, VIII, 133. 



