THE GENERAL CONDITIONS OF LIFE 321 



going an essential change ; these phenomena may be termed 

 histolytic processes. In the other group the normal vital processes 

 are turned into a perverse course by the fatal lesion, and degenerate 

 before they come to a complete standstill. These are termed 

 metamorphic processes. 



1. Histolytic Processes 



The simplest forms of the histolytic processes are the atrophies. 

 They are mostly chronic processes, and consist in the gradual 

 constant decrease in extent and final complete cessation of the 

 ascending phase of the metabolism of the cell in question, that is, 

 of the processes that lead to the construction and regeneration of 

 living substance. The result is that the living substance, con- 

 tinually undergoing decomposition in a certain measure, loses in 

 volume constantly ; the cell becomes constantly smaller, until 

 finally the remnant, having come to an extreme, disintegrates 

 technically speaking, the cell or the tissue " atrophies." 



Cases of atrophy of an organ or tissue are wide-spread in the 

 organic world, and play a great role both in the normal develop- 

 ment of animals and in pathological conditions. 



Among those that appear in the development of the normal 

 organism and are especially well known are the phenomena of 

 histolysis or degeneration of embryonic organs, which are particu- 

 larly characteristic of animals that have a pronounced metamorphosis 

 or larval development. These histolytic processes have been care- 

 fully followed recently in the atrophying tail of the tadpole of the 

 frog by Looss ('89). In its essentials histolysis follows a cor- 

 responding course in different forms of cells. There is notice- 

 able first a loosening of the cement- substance that unites 

 the cells together into the tissue, so that the cells adhere 

 to one another less closely. During this a visible change begins 

 in the protoplasm. " The cell-substance gives up its normal 

 characteristic structure. The spongioplasm, present originally in 

 the form of a more or less pronounced spongy framework and 

 usually capable of staining intensely, draws itself together, the 

 individual strands become thicker, and, finally, the whole dis- 

 integrates into a larger or smaller number of spherical droplets, 

 which lie within the hyaloplasm. The latter stains less or not 

 at all, and has likewise come together into a homogeneous mass." 

 The ground-substance in which the globules lie first begins to 

 dissolve, and later the globules themselves become liquefied. Thus, 

 finally, of the whole protoplasm there remain only a few insoluble 

 granules, and these are devoured by the leucocytes which creep 

 about as phagocytes in all tissues. The nucleus of the cell usually 

 resists destruction considerably longer, but finally becomes the 

 victim of a similar process. Its ground-substance disappears very 



