332 DR. E. KLKIN. 



The same distinction into a sheath and a central bundle 

 of fibrils exists also in the part between two varicosities, 

 with this difference, that the sheath is thinner and the annu- 

 lar thickenings are scarcer and not so distinct. Those fibres 

 which in a greater portion, especially next the nucleus, do 

 not possess any varicosities, exhibit the transverse rings of 

 the sheath with great uniformity. When looked at in pro- 

 file this appearance is in some respects similar to that of 

 meduUated nerve fibres (Lantermann, MacCarthy), and espe- 

 cially of preparations of nerves prej)ared with chrotnate of 

 ammonia, as described by MacCarthy (1. c.j But in our 

 muscle-fibres the transverse markings being due to rings 

 may be followed over the upper as well as lower surface nf 

 the fibre, which of course is not the case in the medullated 

 nerve-fibre where those markings are due to rods placed ver- 

 tically to the long axis of the fibre. 



fin fig. 17, a and b, the muscle-fibres have not been represented in their 

 whole length, as this would have occupied too great a space, and therefore 

 the varicosities which are especially distinct, and sometimes of a very 

 regular distribution near the extremities of" the fibre, are not shown suffi- 

 ciently numerous.] 



The sheath with its transverse markings is visible also 

 on the thickest part of the muscle-fibre, i.e. the part that 

 includes the oval nucleus. Fur the demonstration of the 

 transverse markings all specimens are useful, hgematoxyliu 

 specimens, however, being best. The distinction between a 

 sheath with annular thickenings and a central bundle of 

 fibrils, is shown with remarkable clearness in some muscle- 

 fibres in which that bundle had shrunk away from the sheath, 

 and thus presents itself as a wavy or more or less zigzng 

 group of fibrils within the latter. In the accomjianying 

 aj woodcut ih), a portion of such a muscle-fibre is shown. 



Within the limiting membrane of the nucleus of every 

 muscle-fibre we notice the very distinct intranuclear network 

 ofjibrils. This network is staitied in our specimens, whereas 

 the ground-substance is in most instances quite transpiirent 

 and unstained ; in a few instances I have seen it, however, 

 assuming a slight tint. There arc muscle-fibres to be met with 

 which, instead of a single oval, possess a constricted nucleus, 

 the constriction being phiced either transversely or, more 



