371 



preparations are preserved in a mixture of glycerine 100 and 

 formic acid 1, at the end of some weeks may be perceived 

 upon each plate a rectangular surface, more deeply coloured, 

 which rejDresents the nucleus. Moreover, these cells may 

 be restored to their primitive form by means of experiment. 

 Upon a living animal, it suffices to pass a thread into the 

 sheath of the tendons, or to inject into it a solution of iodine 

 or of weak nitrate of silver, then to wait twenty-four or forty- 

 eight hours before killing the animal and making the exami- 

 nation. We find in this experiment another application of 

 this general law, to wit, that irritation restores cells to their 

 embryonic form. 



As has been mentioned above, Henle had perceived in the 

 tendons quadrangular plates arranged in longitudinal series. 

 But, not employing carmine, the application of which to histo- 

 logy was discovered later by Gerlach, he could not distinguish 

 the nucleus, and, in consequence, did not consider them as 

 cells. Moreover, using an imperfect method, he could not 

 discover that these rectangular plates proceeded from unrolled 

 tubular cells, and he was forced to remain in absolute doubt 

 upon the subject of the nature and of the histological sig- 

 nificance of these remarkable elements. He did not even 

 consider them as having a permanent existence, and met 

 with them amidst other evidently similar elements, which he 

 believed to be completely different. If all these precautions 

 which I have suggested be not taken in the pre2)aration of 

 the tendons, in place of the regular forms, the most extra- 

 ordinary figures may be seen. It is imjjortant to pause here 

 for a moment in order to understand completely the import- 

 ance of these methods in histological research. The little 

 tendon being fixed by the two extremities, and examined in 

 acetic acid if it be cut in such a manner as to release it from 

 its ligatures, swells up, recedes and loses a third or half 

 of its length. This retraction is due to the fibrous substance; 

 the cellular tubes do not participate in it ; and in order to 

 compress themselves into a shorter space they are forced to 

 assume zigzag or undulating forms. At times they even 

 twist themselves into corkscrews. It is not to be dou.bted 

 that Henle has taken such figures for fibres of nuclei, and 

 for spiral fibres. When, before allowing the tendons to curl 

 up under the influence of acetic acid, they have been com- 

 pressed in such a way that the tubular cells are unrolled, at 

 the moment of retraction it may be observed that the cells, 

 and especially their nuclei, are thickened lengthwise. These 

 last, formed, as we have seen, by an extremely fine lamina, 

 become plicated transversely, and appear striped (fig. 2). 



