442 THE SALIVARY GLANDS, BY E. F. W. PFLUGER. 



crease in the transparency of the protoplasm, and this portion 

 occupies a segment made up of from one-fourth to one-third of 

 the spherical volume of the cell (fig. 88). I have not seen the 

 nucleus in this segment, but in the remaining more darkly 

 granular portion. The nerve tears across with remarkable 

 facility at the point of its insertion, which appears to be ex- 

 tremely soft, and hence leaves no trace of the point at which 

 it was attached to the cell. This may be reasonably attributed 

 to the fact that the connection is only effected by means of the 

 axis cylinder, which, whilst it is continuous with the semi- 

 fluid protoplasm of the cell, undergoes no sudden interrup- 

 tion at this point. It is on this account impossible, without 

 appropriate, though necessarily very slight, hardening with 

 reagents, to bring into view the isolated fresh salivary cells, 

 with their associated nerve fibres. It is not surprising that 

 the medullated primitive fibres are sometimes very fine, some- 

 times very thick, when we know that the epithelial cells 

 gradually increase to substantial structures, from minute no- 

 dules on extremely fine axis-cylinder fibrils. With their 

 increase the size of the nerve also augments ; it acquires a 

 medulla, and becomes progressively thicker. It is this circum- 

 stance in part, and partly the fact already mentioned, that, on 

 the application of pressure or other form of mechanical vio- 

 lence, the medulla separates from the dark-edged primitive 

 fibres, whilst the axis cylinder breaks up into fibrils pene- 

 trating the protoplasm of the salivary cells, that forbids us 

 any longer to regard the latter mode of nerve termination as 

 peculiar. 



Whether this holds for all pale nerve terminations found in 

 the alveoli appears to me, from the stand-point obtained in the 

 physiological experiment demonstrating that two kinds of 

 nerves exert an action upon the gland, to be doubtful. There 

 may in particular be found well-preserved long tubes, ap- 

 parently composed of connective tissue, the wall beset with 

 nuclei, continuous with the membrana propria of the aveoli, 

 and containing one or more fine fibrils, that are lost in the 

 gland vesicles. They rarely occur in comparison with the 

 medullated fibres, but are more stable on account of their 

 sheath, so that they alone can be seen in some of the modes 



