EIGHTH LECTURE. 



MUSCULAR TISSUE. 



We now return to the mid- 

 dle germinal layer of the em- 

 bryonic germ, and discuss one 

 of its most important and 

 extensive productions ; we 

 refer to the -muscular tissue. 



This presents, in man and 

 the higher animals, two quite 

 different appearances. In the 

 one we recognize as elements 

 elongated, spindle-shaped cells 

 of a homogeneous appear- 

 ance (Fig. 74) ; in the other 

 we meet with a longer, larger, 

 striated fibre (Fig. 75, a). 



One speaks, accordingly, of 

 smooth and transversely stri- 

 ated muscles. Do not believe, 

 however, that we have here to 

 do with two entirely different 

 things ! In the first place, we 

 meet with quite a number of 

 intermediate varieties in the 

 great multiform animal world ; 

 and then the two different 

 representatives of the mus- 

 cular tissue originate from ex- 

 tremely similar initial struc- 

 tures. The smooth element 



Fig. 74. — Smooth muscular tissue of man 

 and the mammalia , a, a developing cell from 

 the gastric region of a two-inch long hog's em- 

 bryo ; 6, a more advanced cell ; c to g, various 

 forms of the human contractile fibre cell ; h, 

 one with fat granules ; i, a bundle of smooth 

 muscular fibres ; k, transverse section through 

 such a one from the aorta of the ox, with 

 many nuclei in the plane of the section. 



stops at a lower stage ; the 



