1897] MICROSCOPICAL JOURNAL. 75 



fibrils und l>(;<'ii' a .similar relation to tiic lil)r('s tiiat tin* 

 fasick's do to the iniiscle. 



Each fibre, moreover, contains nuclei. They are oval 

 bodies, the long axis usually i)laced [)aralled with the 

 loni;axis of the fibre (Fig. 3). The [>osition of nuclei varies 

 gieatly in the difierent animal forms and for this reason 

 s[)ecial stress is laid upon it in this discussion. The 

 [loints to be em[)hasized are, the position and number of 

 nuclei imbedded in the sarcous substance and the relative 

 sizes of the different fibres. The animals have been 

 chosen from widely varying classes to give a fair repre- 

 sentation of all types. They are taken up in order, ac- 

 cording to their classification in the animal kingdom. 



The fish representative is an elasmobranch, the dog- 

 fish. Its striped muscle fibre is long and cylindrical as 

 is usual. At its ends it tapers suddenly, the striated 

 condition is lost and only the connective tissue covering 

 stretches out into muscle attachment. The fibres vary in 

 width but an average diameter of twenty fibres, as shown 

 in section, is 74 microns. The nuclei are imbedded in the 

 sar(-0U8 substance and only rarely is one found by the 

 edge, making but eleven per cent of the whole number in 

 this position. 



The frog is the amphibian representative (Fig. 4). 

 The different fibres vary greatly in width, those nearer 

 the outer edge of a muscle section appearing much 

 smaller. This may be due to the tact that the fibres ter- 

 minate on the outer edge in the sheath of muscle. The 

 average diameter of twenty fibres as shown in section is 

 66 microns. The only measurements found mentioned are 

 those given by (rage (Reference Handbook of Medical 

 Science, Vol. V. p ): the approximate width is 56 mi- 

 crons for amphibians. 87 per cent of the nuclei are im- 

 bedded in the sarcous substance. A transection of a 

 fibre shows fVom one to six nuclei. The frog is quite a 



