1881.] the Striation of Voluntary Muscular Tissue. 379 



about, or by twisting the tube of the microscope obliquely, the dots 

 disappear from one part of the fibre to appear in another, showing 

 that it is but an optical effect, and that no structure here exists. 



Before concluding I must gratefully acknowledge much help and 

 sympathy which I have received in this investigation. 



To Professor Tait I have gone when in any difficulty, for an 

 observer in a case such as this must have the aid of an experienced 

 physicist, otherwise grievous error is but courted. To him, as has 

 been seen in the text, I owe many suggestions, and he has kindly 

 entirely looked over my paper. Dr. Klein has shown me great kind- 

 ness in carefully examining my preparations from the histological 

 point of view, and as has before been mentioned, in showing me pre- 

 parations to corroborate my views. My thanks are also due to my 

 friend Mr. John Priestley, for many hints, especially concerning the 

 literature of the subject. 



DESCRIPTION OF PLATE 5. 



Figure 1. This represents a muscular fibre viewed with a very high power. The 

 borders are wavy and the cross stripes correspond with these inequalities. 

 (D) marks the positions of Dobie's dark stripes placed in the centres of 

 the depression seen at the border. (H) represents Hensen's stripes, or 

 Dobie's light stripes, placed on the summit of the ridges, in the centre 

 of the dark band. 



Figure 2 shows the appearance of the fibre with crossed Mcols. The shaded parts 

 are seen on the slopes between the ridges and depressions. They are 

 explained fully in the text. 



Figure 3. A fibre is represented as seen with three positions of the lens. In (a) the 

 lens is elevated and the depressions appear dark. In (c) the lens is 

 fully depressed when the stripes are reversed, the depressions being 

 now light with Dobie's dark stripe in the centre of them, and the crests 

 dark but with Dobie's light stripe in the midst. In (b) an inter- 

 mediate stage is seen. 



Figure 4. This shows the passage of rays of light through the fibre. The convex 

 parts converge the rays to focus A', A", A"', after which they diverge. 

 The lens shifted up or down (vertically) over the ridges or depressions, 

 will focus on the retina alternately converging and diverging rays. 



Figure 5. Muscular fibres of Echinus, described by Messrs. Geddes and Beddard. 



Figure 6 represents a nucleus seen by me, which impressed on the muscle, is 

 moulded to the same shape and appears to be cross striped. 



Figure 7 shows the striping of the muscular tissue of the heart. 



