360 R. R. BENSLEY 



portion of acetic acid, as for example, Hermann's and Flemming's 

 fluids 'and the solutions mentioned above. In preparations 

 fixed in Benda's fluid the acini at the margin show a homogeneous 

 basal substance while those farther and farther from the margin 

 show the basal filaments more and more clearly. On the con- 

 trary, the filaments of Michaelis and Altmann become less and 

 less apparent as one studies acini farther and farther from the 

 margin in Benda preparations, which is a sufficient indication 

 of a profound modification of the cytoplasm associated with the 

 appearance in it of the basal filaments of Solger. I am therefore 

 inclined to the opinion that the basophile filaments of Solger are 

 fixation artefacts produced by acid precipitation, and that the 

 real basal substance of these cells is homogeneous. It is quite 

 possible, however, that the basal filaments are preexistent in the 

 living cell though invisible because they are imbedded in a sub- 

 stance of the same refractive index, and that they are rendered 

 visible in the acid fixations by contraction. On this basis it would 

 be necessary to assume that the filaments are swollen in the chrome 

 sublimate, and formalin Zenker preparations, so as to occupy 

 apparently all the space in the cell not taken up by filaments of 

 Altmann, or fat globules. 



Fig. 11 shows an acinus from a preparation fixed in acetic 

 osmic bichromate, and stained in Altmann's anilin acid fuchsin, 

 followed by differentiation in methyl green. In this preparation 

 the filaments of Michaelis and Altmann show as distinct bacillus- 

 like filaments, located for the most part in the basal portion of 

 the cell and surrounded by a homogeneous basal substance. In 

 these preparations the filaments are stained intensely red, the 

 basophile substance green. The zymogen granules are also 

 stained intensely red. This preparation corresponds exactly 

 with what is seen in the living cell, and is the positive image where 

 fig. 10 represents the negative. 



Here, in particular, the filaments of Michaelis and Altmann 

 require comment. These filaments were first observed in fixed 

 material by Altmann ('94), who called them elementary filaments 

 or vegetative filaments and who supposed that they were endowed 

 with the power of growth, and of forming zymogen granules. 



