564 Journal of Applied Microscopy. 



but is so closely similar to a ciliated epithelium that it shows similar structure. 

 The author worked out for these cells a schematic form which he calls a four-sided 

 column, with so large a nucleus as to nearly fill the cell. Plasma fibrils begin at the 

 free end of the cell and pass to the opposite end, not, however, surrounding the 

 nucleus entirely, but passing on three of the four sides, and crowding the nucleus 

 slightly closer to the wall on the fourth side where the fibers are not present. 

 These fibers were clearly seen to divide dichotomously, passing from the base 

 outward, and form a cone or pencil incomplete on the one side. Ciliated cells 

 from the liver passages of Helix were fixed in sublimate and stained in iron 

 haematoxylin. These cells are either high cylindrical or flat in shape, but only 

 the first kind were used in these studies. In this kind, many of the cells had 

 entirely lost the general body substance, so that the fibrous part was naturally 

 isolated. The basal bodies are very clearly developed, and a surface view of 

 such cells shows them as spots, sometimes regularly and sometimes irregularly 

 placed, and occasionally several are connected to form a continuous line. The 

 author considers the fibers to form a beautiful example of Englemann's fibrous 

 spindles. 



A surface view of the disc, though not satisfactorily obtained in actual section, 

 is well seen in optical section, and gives an appearance corresponding exactly 

 to Cohnheim's areas in a cross-section of striated muscle. This observation 

 brings the author to a general consideration of the transition between histologi- 

 cal and molecular structures. He states that it is merely one of degree, not at 

 all one of kind, and continues with a clearly drawn illustration from the structure 

 of muscle. He shows that there is great difficulty in defining and designating a 

 muscle fibril. Authors disagree as to what is the ultimate unit, and even the 

 application of very high magnifications will not definitely solve the question, 

 beyond the structure first recognized under moderately high powers. All 

 resolution tends to simply show finer and finer subdivision of a similar nature, 

 but no new or definite unit. In short, the only unit that can be reached beyond 

 is the ultimate contractile unit, and this the microscope cannot discover. But 

 the whole process is one of repeated subdivisions of Cohnheim's areas into 

 smaller and smaller parts ; there is no intermediate unit. Englemann's contract- 

 ile units, the " Inotagmen," are these last molecules, and series of these arranged 

 in rows form progressively larger and larger masses, until finally the range of 

 microscopic visibility is reached, hence the structure seen but represents a mass- 

 ing of " Inotagmen " in strands. A single primary row of these units is assumed to 

 be capable of assimilation, growth, and division ; in this way masses arise that 

 vary much in size. In other words, as the author puts it, the genetic signifi- 

 cance of Cohnheim's areas lies in that there have arisen in the same field his- 

 tological fibrils of higher or lower " orders," from the same original mother 

 fibril or series of " Inotagmen." Again, he defines a muscle fibril as being what 

 in each special case, with the given optical staining or other technical aids avail- 

 able, can be isolated from the metamicroscopic, fibrous structure of muscle as a 

 visible fibrous unit. The histological unit in muscle tissue is simply determined 

 by its visibility ; there is practically no structural change from the first series of 

 " Inotagmen " to the full-sized fiber. 



