TISSUES, ORGANS, AND SYSTEMS. 07 



child not a single true elastic fibre, since even those of the 

 I'xjt. nucha, of the ligt. flava, and of the aorta, when largest, do 

 not measure more than 0*0008 — "OOr". This circumstance 

 alone, might, if we take into account the close resemblance of 

 the elastic and so-called nucleus-fibres in other respects, be 

 considered as a demonstration that the former are also deve- 

 loped out of cells, but we have in addition direct evidence that 

 this is their mode of development. 



In the aorta, in the ligt. nucha, and in the fascia super - 

 ficialis abdominis of human embryos of the fourth and fifth 

 months, we find the same short fusiform cells as in the common 

 connective tissue ; and their coalescence into originally finer 

 fibres, though perhaps not quite so readily demonstrable as 

 in the former localities, may yet be made out with certainty, 

 so that the agreement in their genesis of the finer with the 

 coarser elastic fibres, may be considered to be established. 



Not, however, to the same extent, as with regard to the 

 genesis of the finer elastic fibres, can I agree with the authors 

 mentioned in other points. In the first place, concerning the 

 physiological import of the so-called nucleus fibres, I grant to 

 Yirchow that even in the adult, in some places, they appear to 

 retain more their original character of a system of canals ; yet 

 I can by no means allow, that these nucleus-fibres are to be 

 regarded as a system of tubules subserving nutrition. In 

 my opinion, all fine elastic fibres, which no longer pre- 

 sent any trace of the original cell, i. e. those of the areolar 

 connective tissue of the corium, fascia, of the perimysium, of 

 the periosteum, of the dura mater, of the serous membranes, 

 of the walls of the vessels, and of mucous membranes, are 

 solid fibres, and only of service to the organism so far as 

 they are elastic. 



A relation to nutrition can only be supposed of those elastic 

 elements of the tendons, ligaments, and of the cornea, which 

 present conditions more nearly embryonic ; but even with 

 respect to these it does not appear so evident that it can be 

 decidedly affirmed. In the tendons and ligaments, for in- 

 stance, it is plain that a part only of the elastic elements are 

 not quite fully developed, so that possibly cavities may still 

 exist in them; while the rest, much more considerable, are as 

 completely developed as elsewhere, and oflfer no trace of a cavity. 



