230 E. A. Schäfer, 



muscle-segment of the leg-muscles, have an actual existence as such; 

 or whether in every case in which their presence has been described, 

 they do not owe their appearance to sarcoplasmic accumulations. It 

 might be thought an easy matter to determine, whether the dots or 

 granules which have been described as accessory „disks" are situated 

 in the line of the sarcoplasmic interstices, or in the course of the sar- 

 costyles. It is sufficiently easy to determine this point in acid and 

 acid-gold preparations of muscle. There is no question whatever that 

 the dots seen under these conditions are sarcoplasmic and do not 

 belong to or occur in the course of the sarcostyles themselves. The 

 difficulty is with alcohol preparations of muscle in which the substance 

 of the sarcous elements has become, from the coagulation and shrink- 

 ing which has been produced by the reagent, much more strongly 

 refracting than before, so that the principal cross-stria appears to be 

 made up of rod-like elements set side by side, with clear interstices, 

 while in the light striae are sometimes seen the rows of granules 

 which have been there described as the accessory disks. Nevertheless. 

 the results of careful observation with the highest powers have 

 always seemed to me to point to the fact that the granules are 

 truly inter-columnar and are therefore sarcoplasmic. I have taken the 

 more pains to assure myself upon this point, because my observation 

 is in disaccordance not only with the statements of Flögel and Engel- 

 mann, who were unacquainted with the existence of the sarcoplasmic 

 accumulations, but also with some of the descriptions and figures given 

 by Eollett, whose statements and observations regarding the structural 

 appearances of muscle I have otherwise uniformly found to be 

 accurate. Tliis conclusion I have arrived at in adopting the 

 method which Rollett particularly recommends for the clear demon- 

 stration of the accessory disks as structures distinct from the sar- 

 cous elements (principal disks). The method consists in the 

 cautious addition of formic acid to the alcohol preparation under the 

 microscope, and the continuous observation of the changes which it 

 produces. According to Rollett the reagent first produces a swelling 

 of the sarcous elements (Querscheibe) so that these bulge out beyond 

 the line of the granules which he describes as representing the 



