272 ON GROWTH AND OVERGROWTH 



cannot be regarded as due to proliferation of the atrophied cells 

 — their relative position forbids such an assumption. Their 

 existence, however, is strongly in favour of the view that they 

 have been derived from mother cells in the grey substance. 



The regeneration of nerve fibres is another matter. So far 

 as regards the axones, or axis-cylinder processes themselves, it 

 is strictly comparable with the new growth of the cell substance 

 of the amoeba when a part of that cell substance has been removed 

 without direct injury to the nucleus. As regards the investing 

 sheath of the medullated nerve fibre, regeneration here is in 

 strict accordance with the third law ; there is a preliminary 

 period of reversion ; the formed substance (myelin), governed 

 or elaborated by the cell, breaks down, the nuclei become more 

 prominent and surrounded by an increased amount of protoplasm, 

 and then in place of a single nucleus of a node of Ranvier one 

 gets numerous nuclei, and the new cells evidently surround the 

 newly developed axis cylinder as it grows downwards from the 

 seat of injury. 



I have already referred to the regeneration of muscle, but if 

 we now pass to the other extreme and consider what happens in 

 the simplest of all tissues, namely, white fibrous connective 

 tissue, we find that even here for pathological regeneration to 

 occur there is a preliminary stage of swelling of the connective 

 tissue cells, the nuclei become larger and more prominent, the 

 surrounding protoplasm becomes increased in amount, the 

 surrounding fibrils tend to disappear, and now, only after this 

 reversion to a simpler, more embryonic condition, do we have 

 proliferation and the subsequent building up of new connective 

 tissue. 



To enter here into a discussion as to whether connective 

 tissue can be formed from wandering cells, and whether any 

 special form of wandering cell is capable of taking part in such 

 new formation, would be imperative if I were dealing more 

 especially with the law that tissues arise from pre-existing specific 

 tissue cells ; here rather, dealing with the process and the law 

 of growth, with the law of mother cells, if I may so term it, the 

 very limits to which this article is confined must be an excuse 

 for not dealing with this subject. 



