300 



Dr. J. B. Hay era It. 



The Interfilrillur Substance. 



The interfibrillar substance is not usually held to have the propc 

 of contractility, aud it appears to me that the arguments based on 

 its fancied homology to a cell network recently brought forward, espe- 

 cially in England, can hardly be said to prove the contrary ; I hope to 

 refer to this subject in a subsequent paper, to be devoted to the com- 

 parative histology of muscle. From the varicose character of the 

 fibrils, it follows that the interfibrillar substance is of the nature of a 

 matrix or bed of tissue perforated by varicose tubes. It is like 

 honeycomb minus its transverse partitions, or, better still, like 

 mitrailleuse ; we have, however, to imagine the walls of the honej 

 comb of variable thickness, sometimes thicker and sometimes thinne 

 and the analogy is complete. In optical section, as when we fc 

 a piece of muscle, this interfibrillar honeycomb will appear as 

 photograph I or fig. 5. 



FIG. 5. 



Two fibres are represented, A and S. The interfibrillar substance is sti 

 represented by the varicose lines ; the outlines of the fibrils are faintly 

 sented at the borders of the figures. In A the fibrils possess well- 

 Dobie's lines ; the swellings of the fibrils causing them are seen, Z>. In 

 sequence, the cement matter forming single masses in B is in A divided 

 two sets (heads of Schafer's muscle rods). In B Dobie's lines are not 

 In diagram the cross-striping! of the fibrils has been omitted for the 

 simplicity. 



Here the fibrils are left blank, and the interfibrillar substance 

 represented by dark varicose lines, the optical sections of the loi 

 tudinal walls of the honeycomb. The walls are thick opposite tl 

 position of the constrictions of the fibrils which lie within the honey- 

 comb, and thin wherejthe bulgings come. When a Dobie's bulge is 

 present as at A, the bulgings, corresponding to the clear strip' 

 divided into two (Schafer's muscle rods) ; but when Dobie's lim- is 

 not well marked, we have the appearance seen at B. Of con; 

 will be understood that where these thickenings of the honeycomb 



