CELLULAR ELEMENTS OF THE GROUND-SUBSTANCE. 23 



The system of cell-plates, with their processes, can be brought into 

 view very distinctly, and without great loss of time, by mounting the 

 preparation in diluted Miiller's fluid, instead of in serum or humor 

 aqueus, and they there become visible in fifteen minutes, or even 

 less. 



Not all of the cells which we have designated above as being 

 branched are flat and of the same size ; generally they are in some 

 degree flattened. The largest of these latter cover nearly the third 

 part of a field (Hastnack |), but there are many which are smaller. 

 The question arises now, in what relation do the first-mentioned 

 granular spindle-shaped cells stand to those branched more or less 

 flattened elements. 



If one compares a number of preparations it is obvious that in 

 some of them the number of spindle-shaped elements is a very great 

 one, and that they mostly run in one direction, whereas in some other 

 ones there are only few to be found. As regards their aspect, these 

 spindle-shaped cells resemble perfectly those which are to be found 

 in embryonal connect ive-tissue. If a preparation of the above-men- 

 tioned substance, containing a great number of spindle-shaped ele- 

 ments, is mounted in a large drop of serum or humor aqueus, and if that 

 edge of the covering glass which lies parallel to the longitudinal axis of 

 a certain number of the spindle-shaped elements is pushed slightly 

 by a needle one can observe the remarkable fact that the coarsely 

 granular spindle-shaped elements become all converted into pale, 

 branched, partly finely-granular partly striated, plates, each of which 

 contains a large flat ovoid nucleus. If, then, the cover-glass is again 

 allowed to float back, the plates become again converted into spindle- 

 shaped elements. 



In preparations which had been mounted only shortly before, the 

 placoids which appear instead of the spindle-shaped elements are 

 very faint, exactly as we saw them previously in fresh preparations, 

 mounted only a very short time. This manipulation proves that the 

 coarsely-granular spindle-shaped elements are not, in fact, spindle- 

 si uiped, but are perfectly identical with the above-mentioned placoids 

 seen edgewise. Under a high power, and using sufficient care, one 

 can easily observe, by the above-mentioned manipulation how an in- 



