CONTRACTILITY OF Till: 1-RAMEWORK 269 



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As has been mentioned, Briicke had already actually 

 postulated a contractile internal framework of firmer con- 

 sistence for the explanation of the phenomena of movement 

 and streaming in protoplasm. When, therefore, Heitzmaun 

 in the seventies had described the reticular framework of 

 protoplasm, he concluded at once that it was a contractile 

 framework of this kind, by alterations in which all the 

 movements of protoplasm could be explained. In his 

 opinion this framework alone is contractile ; the intervening 

 matrix, on the contrary, is a "non-contractile fluid." Dur- 

 ing the contraction of the framework the filaments which 



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connect neighbouring nodal points shorten, owing to the 

 latter at the same time swelling and approaching one 

 another. In accordance with this view Heitzmann was 

 forced to imagine that the substance of the filaments is 

 absorbed by the nodal points as they swell. When the 

 framework is relaxed the reverse process takes place. In 

 addition to this Heitzmann further assumes the occurrence 

 of a condition of extension of the framework, which arises 

 by a squeezing out of the intervening fluid of one region of 

 the protoplasmic body, which is contracted, and its being- 

 driven into another, thereby causing the framework to 

 become stretched beyond the normal condition. As a 

 result of this expansion of the meshes the filaments 

 are said to become greatly elongated, the nodal points 

 reduced to the vanishing point, and the whole meshwork 

 finally so attenuated that it becomes quite invisible, as in 

 the pseudopodia of Amoebre, etc. The protrusion of the latter, 

 as well as phenomena of protoplasmic movement in general, 

 he thus explains by a local stretching of the framework 

 in this manner as the result of local contractions. 



Most of the adherents of the framework theory were, on the 

 whole, in agreement with Heitzmann, to the extent at least that 

 they in like manner considered the framework, or the fibrilla? 

 of the protoplasm, as the contractile elements, and sought in them 

 the seat of the locomotory phenomena, changes of form, processes 

 of division, etc. A more precise analysis of the processes wa- 



