THE HIGHER ANIMAL TISSUES. 79 



possessing any excretory duct in the ordinary sense of 

 the word, but also because from the mode of their deve- 

 lopment they by no means occupy the same position 

 as ordinary glands, but are on the contrary at every 

 period of their existence nearly allied to the connective 

 tissues, and that, therefore, the temptation would rather 

 be to class them with the tissues which we see produced 

 by the transformation of the connective tissues. Yet 

 this would at the present moment be still rather a ven- 

 turous undertaking. 



Amongst all the forms of which we have here to treat, 

 the elements of muscle have generally been regarded as 

 the most simple. If we examine an ordinary red muscle 

 (I do not say a voluntary one, inasmuch as in the heart 

 also we meet with fibres of the F m. 23. 



same form) we find it to be essen- 

 tially composed of a number of 

 cylinders, for the most part of 

 equal thickness (primitive fasci- 

 culi [fibres]), which on a trans- 

 verse section are seen to have a 

 cylindrical form, and on which we 

 at once perceive the well-known 

 transverse striae, that is, broad 

 lines which generally run transversely through the fasci- 

 culus with a somewhat wavy outline, and are almost as 

 broad as the intervals that separate them. In addition 

 to this transverse striation we also see, especially when 

 certain modes of preparation have been adopted, strise fol- 



Fig. 23. A group of primitive muscular fasciculi [fibres], a. The natural appear- 

 ance of a fresh primitive fasciculus, with its transverse striae (bands or discs)t 6. 

 A fasciculus gently acted upon by acetic acid ; the nuclei stand out distinctly, and 

 in one of them two nucleoli are visible, whilst in another the division is complete. 

 c. A fibre acted upon more strongly by acetic acid ; the contents are swollen up at 

 the end, so as to protrude from the sheath (sarcolemma). d. Fatty atrophy. 800 

 diameters. 



