88 



EIGHTH LECTURE. 



In small embryos one obtains thin (0x045 to 0.0068 mm.), 

 but long (0.28 to 0.38 mm.) spindle cells, with one or 

 two vesicular nuclei, and in the centre commencing for- 

 mations of transverse lines, that is with a transformation 

 into sarcous elements. With an increase in nuclei, the 

 structure increases not only in length but also in breadth. 

 The transverse striation advances towards the ends, but leaves 

 the axial portion still free. We still meet here with the old 

 protoplasm. Later, however, after the longitudinal markings 

 have also appeared, this protoplasma has disappeared, with 

 the exception of a slight residue, which surrounds the nucleus 

 and thus forms the muscle corpuscle. We find the latter, at 

 last, in mammalia and man, displaced towards the periphery. 

 We have already above (p. 82), declared the sarcolemma 

 of the transversely striated filament to be a homogeneous 

 boundary layer furnished by the adjacent connective tissue. 

 All investigators do not, however, coincide with our view. 



The muscular filaments of the new born are still much finer 

 than those of the adult. The subsequent increase in thick- 

 ness explains in great part the growth of the 

 muscle in transverse diameter. New fibres 

 are also subsequently developed (Budge). 

 This has, it is true, been recently disputed. 

 Weismann observed that the muscles of 

 the frog divide in a longitudinal direction, 

 with a prodigious increase in their nuclei. 

 One then sees regular columns of nuclei de- 

 scending near each other. The filament di- 

 vides, one becomes two, which subsequently 

 acquire the normal diameter by a growth in 

 thickness. The two products of division 

 may afterwards repeat the same cleaving pro- 

 cess. A single muscular filament may in this 

 way finally become a whole group of filaments. 

 Among the forms of retrogression of 

 our tissue, fatty degeneration is the most frequent (Fig. 85). 



Fig. 85.— Fatty degen- 

 erated human muscular 

 fibre ; a, slighter ; /;, 

 increased ; c, highest 

 degree. 



