THE MUSCULAU SYSTEM. 



273 



striae, and even with fibrils, which 

 It is partially evident, even in a Ion- 

 Fig. 105. Fig. 106. 



I 



ll 



tudinal and transverse 

 admit of being isolated. 

 gitndinal view, but 

 still better in a trans- 

 verse section, that 

 in many cases, the 

 fibrils do not occupy 

 the entire thickness 

 of the primitive tube, 

 but that they are 

 deposited around its 

 periphery, the inte- 

 rior being as yet filled 

 with a homogeneous 

 substance as at first, 

 and which now ap- 

 pears like a canal 

 within the fibrils. 

 All the primitive tu- 

 bules possess a sar- 

 colemma {b), which 

 on the application of acetic acid or soda, appears as a 

 very delicate membrane, which by the imbibition of water, 

 may occasionally be raised from the fibrils. The tubes, 

 moreover, as at first, present nuclei lying close upon the 

 sarcolemma, and which frequently cause rounded elevations 

 on the surface of the tube, and may be observed actively 

 engaged in the process of multiplication. They are all 

 vesicular, roundish, or elongated, with very distinct, simple or 

 double nucleoli measuring 0*0004 — O'OOOS'", and frequently 

 with two secondary cells in the interior. They are much more 

 numerous than previously,, and most frequently disposed in 

 pairs closely approximated ; but often, also in groups of three 



Fig. 105. Primitive fasciculi of an eight to nine weeks' human -embryo, x 350 

 diam.: 1, two fibres without transverse striae ; 2, fibres presenting the first indications 

 of transverse striation ; a, nuclei. 



Fig. 106. Primitive fibres of a four-months' human embryo, x 350 diam.: 1, a 

 fasciculus, with a clear, as yet, non-fibrillated substance in the interior : 2, fasciculus 

 without such contents, with an indication of transverse striation; a, nuclei; b, sar- 

 colemma. 



i. 18 



