136 H. F. Lueders — Structure of Caoutchouc. 



of examining, shown the presence of rubber globules still 

 distinct in the mass, although Wiesner* states that he distin- 

 guished them in one variety. 



But even if solidification obliterates all traces of the orig- 

 inal globules, does not the rubber in its solid state show a 

 structural arrangement common to all its varieties ? 



Payenf claims for it an irregular reticulated structure, 

 Wiesner;£ finds also many cases of reticulation, though also 

 some where only a crumpled foliar structure was visible. 

 Faraday on the other hand regards rubber as structureless. 

 Of the twenty specimens which I examined no two agreed in 

 their microscopic structure ; three main types might, however, 

 be distinguished. Namely (1) the blistery flowage (2), the 

 reticulated, and (3) the stratified. Reticulation proves of in- 

 frequent occurrence, while stratification predominates. The 

 coarse stratification can generally be shown to be parallel to 

 the surface of the rubber mass, while solidifying. Most strat- 

 ified specimens showed a system of crumpled, branching, or 

 broken crosslines, such as might be formed by the shrinking 

 of any drying layer. In some of the stratified specimens, 

 peculiar illusory appearances are discernible resembling roughly 

 the structure of wood-cells of certain conifers or in a few cases 

 ducts of angiosperms. These misleading appearances are pro- 

 duced by particles of included dust, fragments of wood bark, 

 and the like. 



Different parts of the same sample are frequently found to 

 possess unlike structure. These facts lead us to doubt not 

 only the presence of a definite structure common to all kinds 

 of rubber, but also of any structure distinctively peculiar to 

 each one. 



In order to place the above statement on. a yet firmer basis 

 I made chloroform solutions of various varieties of rubber. 

 These were allowed to solidify and then sectioned and ex- 

 amined. Various markings were found, but none similar to 

 those of the respective varieties before dissolving. 



Caoutchouc then has no definite structure, per se, and all 

 apparent structure is only the result of the conditions under 

 which its coagulation from the latex, and subsequent solidifica- 

 tion take place. 



In "Wiesner's discussion of the microscopic properties of 

 rubber, occur the following statements: "all varieties of rub- 

 ber so far as examined by me, appeared, between the Nicols 

 of the polarizing microscope, in brilliant colors." " The polar- 

 ization colors appear most striking if a thin section of caout- 

 chouc is strongly compressed between two slides."* 



* Wiesner. Rohstoffie des Pflanzenreiclies, p. 158. f Compt. Rendus, xxxiv. 

 % Rohstoffe, p. 164. § Rohstoffe, pp. 164, 165. 



