336 THOMAS J. HELDT 



fibrillae however are best observed in preparations frozen quite 

 rapidly and at moderately low temperatures (—5° to — 15°C.), 

 for when thus treated the intracellular neurofibrillae do not seem 

 to take part in the fonnation of the cellular reticulum corre- 

 sponding to that stained with toluidin-blue and erythrosin. At 

 temperatures below the foregoing, especially if frozen slowly, the 

 intracellular neurofibrillae cannot be made out with any degree 

 of certainty though they are still quite distinct in many of the 

 cell processes and in the fine nerve fibers of the intercellular 

 spaces. The above observations were made on smears frozen 

 and fixed forty-two seconds after decapitation and at different 

 times afterwards up to twenty-five hours after death. These 

 observations on the neurofibrillae in frozen tissue are quite in 

 agreement with Liesegang's ('11) conception; but, on the other 

 hand, quite opposed to that of Auerbach ('11). 



In the above study of neurofibrillae both in the unfrozen and 

 the frozen preparations many ^'ariations were met with. In this 

 regard, as Legendre ('06), Marinesco ('09), and many others 

 have noted, it may be mentioned that the methods for the dem- 

 onstration of neurofibrillae are not sufficiently adequate or relia- 

 ble to permit of constant results. Only by extensive observation 

 and many controls can definite conclusions be reached. So it 

 may be questioned whether the above observations on the neuro- 

 fibrillae in frozen nerve cells, in this one investigation, are suffi- 

 cient to determine the point at issue; yet, since this point is 

 merely the presence of the neurofibrillae in such frozen cells, 

 without reference to the details of their distribution, and so 

 forth, the author believes the results may be regarded as quite 

 reliable. 



It may be of interest to note that both the Nissl's bodies and 

 the neurofibrillae were unmistakably present in ner\'e cells from 

 the cervical portion of the spinal cord of horse (cf. 'Material 

 and technique'), fixed three minutes after the instant of the shoot- 

 ing of the animal. 



In imbedded tissue, that is, tissue fixed, dehydrated, imbedded 

 in paraffin (or celloidin), cut, stained, and mounted; both the 

 Nissl's bodies and the neurofibrillae were clearly and distinctly 



