142 THE MITOCHONDRIAL CONSTITUENTS OF PROTOPLASM. 



mitochondria; in other words, that mitochondria are associated in the production 

 of starch and chlorophyll and a great variety of other substances. 



(8) And finally, their intensive study in so many cells of both animals and 

 plants has resulted in a well-marked movement toward the study of the whole cyto- 

 plasm and many facts of importance, not directly related to mitochondria, have 

 been brought to light. It has forced, for instance, a complete readjustment of 

 our conception of protoplasm. 



(a) Flemming's filar theory.— According to this hypothesis, jirotoplasm con- 

 sists fundamentally of a homogeneous ground-substance in which fibrils are em- 

 bedded. The relatively dense and refractile fibrils he called the mitome and the 

 watery fluid between them the paramitome. The idea has been much modified 

 by himself and others. Now that we are in a better position to understand his 

 fila, we reaUze that they are a very heterogeneous group of structures. Many of 

 them are artifacts and others mitochondria. He included under the same head- 

 ing such widely different structures as spindle fibers. This mere separation of 

 protoplasm into mitome and paramitome helps but Uttle. 



(6) Altmann's bioblast theory.— Mtmaim observed (in many varieties of cells) 

 minute granular rod-like and filamentous structures which he took to be elementary 

 organisms. He thought that they existed in the form of colonies in cells and that 

 they multiplied by di\-ision. He formulated the statement omne granulum e 

 granulo. According to him they constitute the vital hving substance as contrasted 

 with the lifeless inert ground-substance containing them, in token of which he 

 called them "bioblasts." Recent work on the bioblasts has robbed them of 

 all their mystery. They are in reahty a heterogeneous class of cell granulations 

 Uke Flemming's fila, no more living than the rest of the cytoplasm and comprising 

 mitochondria for the most part, but some fat, pigment, and secretion antecedents 

 in addition. We can see now Altmann's many mistakes as well as appreciate the 

 element of truth in his conception, for mitochondria are in reahty almost universal 

 constituents of protoplasm. 



(c) Fromann's reticular theory.— In terms of tliis hypothesis all protoplasm 

 consists, in the last analysis, of a relatively dense reticulum of fine threads, some- 

 times called spongioplasm, and of a more fluid material in the interstices called 

 hyaloplasm. Contractility of the threads has been invoked to explain movement. 

 Others think that they constitute the origin of fibrillar structures, like myofibrils. 

 Recent studies in cell dissection by Kite and Chambers have failed to reveal the 

 existence of such a reticulum and our knowledge of mitochondria is incompatible 

 with its existence, for we find that they move freely from place to place in the 

 cytoplasm without let or hindrance. Nevertheless the conception persists in our 

 text-books in the form of misleading diagrams which should be eliminated as 

 quickly as possible. 



(d) Butschli's foam theory.— Butschli afforded strong experimental evidence 

 in support of the alveolar theories of the structure of protoplasm, according to 

 which the continuous fundamental substance is composed of alveolar walls and 

 alveolar contents. The foam structure is sometimes visible in the living condi- 



